blob: 6b597cf33b02f4a03b269547b88ae4f8428aab54 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * Fast Userspace Mutexes (which I call "Futexes!").
3 * (C) Rusty Russell, IBM 2002
4 *
5 * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
6 * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
7 *
8 * Removed page pinning, fix privately mapped COW pages and other cleanups
9 * (C) Copyright 2003, 2004 Jamie Lokier
10 *
Ingo Molnar0771dfe2006-03-27 01:16:22 -080011 * Robust futex support started by Ingo Molnar
12 * (C) Copyright 2006 Red Hat Inc, All Rights Reserved
13 * Thanks to Thomas Gleixner for suggestions, analysis and fixes.
14 *
Ingo Molnarc87e2832006-06-27 02:54:58 -070015 * PI-futex support started by Ingo Molnar and Thomas Gleixner
16 * Copyright (C) 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com>
17 * Copyright (C) 2006 Timesys Corp., Thomas Gleixner <tglx@timesys.com>
18 *
Eric Dumazet34f01cc2007-05-09 02:35:04 -070019 * PRIVATE futexes by Eric Dumazet
20 * Copyright (C) 2007 Eric Dumazet <dada1@cosmosbay.com>
21 *
Linus Torvalds1da177e2005-04-16 15:20:36 -070022 * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
23 * enough at me, Linus for the original (flawed) idea, Matthew
24 * Kirkwood for proof-of-concept implementation.
25 *
26 * "The futexes are also cursed."
27 * "But they come in a choice of three flavours!"
28 *
29 * This program is free software; you can redistribute it and/or modify
30 * it under the terms of the GNU General Public License as published by
31 * the Free Software Foundation; either version 2 of the License, or
32 * (at your option) any later version.
33 *
34 * This program is distributed in the hope that it will be useful,
35 * but WITHOUT ANY WARRANTY; without even the implied warranty of
36 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 * GNU General Public License for more details.
38 *
39 * You should have received a copy of the GNU General Public License
40 * along with this program; if not, write to the Free Software
41 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
42 */
43#include <linux/slab.h>
44#include <linux/poll.h>
45#include <linux/fs.h>
46#include <linux/file.h>
47#include <linux/jhash.h>
48#include <linux/init.h>
49#include <linux/futex.h>
50#include <linux/mount.h>
51#include <linux/pagemap.h>
52#include <linux/syscalls.h>
Jesper Juhl7ed20e12005-05-01 08:59:14 -070053#include <linux/signal.h>
Rusty Russell9adef582007-05-08 00:26:42 -070054#include <linux/module.h>
Andrey Mirkinfd5eea42007-10-16 23:30:13 -070055#include <linux/magic.h>
Pavel Emelyanovb4888932007-10-18 23:40:14 -070056#include <linux/pid.h>
57#include <linux/nsproxy.h>
58
Jakub Jelinek4732efb2005-09-06 15:16:25 -070059#include <asm/futex.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070060
Ingo Molnarc87e2832006-06-27 02:54:58 -070061#include "rtmutex_common.h"
62
Thomas Gleixnera0c1e902008-02-23 15:23:57 -080063int __read_mostly futex_cmpxchg_enabled;
64
Linus Torvalds1da177e2005-04-16 15:20:36 -070065#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
66
67/*
Ingo Molnarc87e2832006-06-27 02:54:58 -070068 * Priority Inheritance state:
69 */
70struct futex_pi_state {
71 /*
72 * list of 'owned' pi_state instances - these have to be
73 * cleaned up in do_exit() if the task exits prematurely:
74 */
75 struct list_head list;
76
77 /*
78 * The PI object:
79 */
80 struct rt_mutex pi_mutex;
81
82 struct task_struct *owner;
83 atomic_t refcount;
84
85 union futex_key key;
86};
87
88/*
Linus Torvalds1da177e2005-04-16 15:20:36 -070089 * We use this hashed waitqueue instead of a normal wait_queue_t, so
90 * we can wake only the relevant ones (hashed queues may be shared).
91 *
92 * A futex_q has a woken state, just like tasks have TASK_RUNNING.
Pierre Peifferec92d082007-05-09 02:35:00 -070093 * It is considered woken when plist_node_empty(&q->list) || q->lock_ptr == 0.
Linus Torvalds1da177e2005-04-16 15:20:36 -070094 * The order of wakup is always to make the first condition true, then
Darren Hart73500ac2008-12-17 17:29:56 -080095 * wake up q->waiter, then make the second condition true.
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 */
97struct futex_q {
Pierre Peifferec92d082007-05-09 02:35:00 -070098 struct plist_node list;
Darren Hart73500ac2008-12-17 17:29:56 -080099 /* There can only be a single waiter */
100 wait_queue_head_t waiter;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101
Ingo Molnare2970f22006-06-27 02:54:47 -0700102 /* Which hash list lock to use: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700103 spinlock_t *lock_ptr;
104
Ingo Molnare2970f22006-06-27 02:54:47 -0700105 /* Key which the futex is hashed on: */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700106 union futex_key key;
107
Ingo Molnarc87e2832006-06-27 02:54:58 -0700108 /* Optional priority inheritance state: */
109 struct futex_pi_state *pi_state;
110 struct task_struct *task;
Thomas Gleixnercd689982008-02-01 17:45:14 +0100111
112 /* Bitset for the optional bitmasked wakeup */
113 u32 bitset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700114};
115
116/*
Darren Hartb2d09942009-03-12 00:55:37 -0700117 * Hash buckets are shared by all the futex_keys that hash to the same
118 * location. Each key may have multiple futex_q structures, one for each task
119 * waiting on a futex.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120 */
121struct futex_hash_bucket {
Pierre Peifferec92d082007-05-09 02:35:00 -0700122 spinlock_t lock;
123 struct plist_head chain;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700124};
125
126static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
127
Linus Torvalds1da177e2005-04-16 15:20:36 -0700128/*
129 * We hash on the keys returned from get_futex_key (see below).
130 */
131static struct futex_hash_bucket *hash_futex(union futex_key *key)
132{
133 u32 hash = jhash2((u32*)&key->both.word,
134 (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
135 key->both.offset);
136 return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
137}
138
139/*
140 * Return 1 if two futex_keys are equal, 0 otherwise.
141 */
142static inline int match_futex(union futex_key *key1, union futex_key *key2)
143{
144 return (key1->both.word == key2->both.word
145 && key1->both.ptr == key2->both.ptr
146 && key1->both.offset == key2->both.offset);
147}
148
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200149/*
150 * Take a reference to the resource addressed by a key.
151 * Can be called while holding spinlocks.
152 *
153 */
154static void get_futex_key_refs(union futex_key *key)
155{
156 if (!key->both.ptr)
157 return;
158
159 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
160 case FUT_OFF_INODE:
161 atomic_inc(&key->shared.inode->i_count);
162 break;
163 case FUT_OFF_MMSHARED:
164 atomic_inc(&key->private.mm->mm_count);
165 break;
166 }
167}
168
169/*
170 * Drop a reference to the resource addressed by a key.
171 * The hash bucket spinlock must not be held.
172 */
173static void drop_futex_key_refs(union futex_key *key)
174{
Darren Hart90621c42008-12-29 19:43:21 -0800175 if (!key->both.ptr) {
176 /* If we're here then we tried to put a key we failed to get */
177 WARN_ON_ONCE(1);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200178 return;
Darren Hart90621c42008-12-29 19:43:21 -0800179 }
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200180
181 switch (key->both.offset & (FUT_OFF_INODE|FUT_OFF_MMSHARED)) {
182 case FUT_OFF_INODE:
183 iput(key->shared.inode);
184 break;
185 case FUT_OFF_MMSHARED:
186 mmdrop(key->private.mm);
187 break;
188 }
189}
190
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700191/**
192 * get_futex_key - Get parameters which are the keys for a futex.
193 * @uaddr: virtual address of the futex
Darren Hartb2d09942009-03-12 00:55:37 -0700194 * @fshared: 0 for a PROCESS_PRIVATE futex, 1 for PROCESS_SHARED
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700195 * @key: address where result is stored.
196 *
197 * Returns a negative error code or 0
198 * The key words are stored in *key on success.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700199 *
Josef "Jeff" Sipekf3a43f32006-12-08 02:36:43 -0800200 * For shared mappings, it's (page->index, vma->vm_file->f_path.dentry->d_inode,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 * offset_within_page). For private mappings, it's (uaddr, current->mm).
202 * We can usually work out the index without swapping in the page.
203 *
Darren Hartb2d09942009-03-12 00:55:37 -0700204 * lock_page() might sleep, the caller should not hold a spinlock.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700205 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200206static int get_futex_key(u32 __user *uaddr, int fshared, union futex_key *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700207{
Ingo Molnare2970f22006-06-27 02:54:47 -0700208 unsigned long address = (unsigned long)uaddr;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700209 struct mm_struct *mm = current->mm;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700210 struct page *page;
211 int err;
212
213 /*
214 * The futex address must be "naturally" aligned.
215 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700216 key->both.offset = address % PAGE_SIZE;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700217 if (unlikely((address % sizeof(u32)) != 0))
Linus Torvalds1da177e2005-04-16 15:20:36 -0700218 return -EINVAL;
Ingo Molnare2970f22006-06-27 02:54:47 -0700219 address -= key->both.offset;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220
221 /*
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700222 * PROCESS_PRIVATE futexes are fast.
223 * As the mm cannot disappear under us and the 'key' only needs
224 * virtual address, we dont even have to find the underlying vma.
225 * Note : We do have to check 'uaddr' is a valid user address,
226 * but access_ok() should be faster than find_vma()
227 */
228 if (!fshared) {
229 if (unlikely(!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))))
230 return -EFAULT;
231 key->private.mm = mm;
232 key->private.address = address;
Peter Zijlstra42569c32008-09-30 12:33:07 +0200233 get_futex_key_refs(key);
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700234 return 0;
235 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200237again:
Peter Zijlstra734b05b2008-09-26 19:32:22 +0200238 err = get_user_pages_fast(address, 1, 0, &page);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200239 if (err < 0)
240 return err;
241
242 lock_page(page);
243 if (!page->mapping) {
244 unlock_page(page);
245 put_page(page);
246 goto again;
247 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700248
249 /*
250 * Private mappings are handled in a simple way.
251 *
252 * NOTE: When userspace waits on a MAP_SHARED mapping, even if
253 * it's a read-only handle, it's expected that futexes attach to
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200254 * the object not the particular process.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255 */
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200256 if (PageAnon(page)) {
257 key->both.offset |= FUT_OFF_MMSHARED; /* ref taken on mm */
Linus Torvalds1da177e2005-04-16 15:20:36 -0700258 key->private.mm = mm;
Ingo Molnare2970f22006-06-27 02:54:47 -0700259 key->private.address = address;
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200260 } else {
261 key->both.offset |= FUT_OFF_INODE; /* inode-based key */
262 key->shared.inode = page->mapping->host;
263 key->shared.pgoff = page->index;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700264 }
265
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200266 get_futex_key_refs(key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200268 unlock_page(page);
269 put_page(page);
270 return 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271}
272
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200273static inline
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200274void put_futex_key(int fshared, union futex_key *key)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275{
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200276 drop_futex_key_refs(key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700277}
278
Darren Hart4b1c4862009-04-03 13:39:42 -0700279/**
280 * futex_top_waiter() - Return the highest priority waiter on a futex
281 * @hb: the hash bucket the futex_q's reside in
282 * @key: the futex key (to distinguish it from other futex futex_q's)
283 *
284 * Must be called with the hb lock held.
285 */
286static struct futex_q *futex_top_waiter(struct futex_hash_bucket *hb,
287 union futex_key *key)
288{
289 struct futex_q *this;
290
291 plist_for_each_entry(this, &hb->chain, list) {
292 if (match_futex(&this->key, key))
293 return this;
294 }
295 return NULL;
296}
297
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700298static u32 cmpxchg_futex_value_locked(u32 __user *uaddr, u32 uval, u32 newval)
299{
300 u32 curval;
301
302 pagefault_disable();
303 curval = futex_atomic_cmpxchg_inatomic(uaddr, uval, newval);
304 pagefault_enable();
305
306 return curval;
307}
308
309static int get_futex_value_locked(u32 *dest, u32 __user *from)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700310{
311 int ret;
312
Peter Zijlstraa8663742006-12-06 20:32:20 -0800313 pagefault_disable();
Ingo Molnare2970f22006-06-27 02:54:47 -0700314 ret = __copy_from_user_inatomic(dest, from, sizeof(u32));
Peter Zijlstraa8663742006-12-06 20:32:20 -0800315 pagefault_enable();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700316
317 return ret ? -EFAULT : 0;
318}
319
Ingo Molnarc87e2832006-06-27 02:54:58 -0700320
321/*
322 * PI code:
323 */
324static int refill_pi_state_cache(void)
325{
326 struct futex_pi_state *pi_state;
327
328 if (likely(current->pi_state_cache))
329 return 0;
330
Burman Yan4668edc2006-12-06 20:38:51 -0800331 pi_state = kzalloc(sizeof(*pi_state), GFP_KERNEL);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700332
333 if (!pi_state)
334 return -ENOMEM;
335
Ingo Molnarc87e2832006-06-27 02:54:58 -0700336 INIT_LIST_HEAD(&pi_state->list);
337 /* pi_mutex gets initialized later */
338 pi_state->owner = NULL;
339 atomic_set(&pi_state->refcount, 1);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200340 pi_state->key = FUTEX_KEY_INIT;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700341
342 current->pi_state_cache = pi_state;
343
344 return 0;
345}
346
347static struct futex_pi_state * alloc_pi_state(void)
348{
349 struct futex_pi_state *pi_state = current->pi_state_cache;
350
351 WARN_ON(!pi_state);
352 current->pi_state_cache = NULL;
353
354 return pi_state;
355}
356
357static void free_pi_state(struct futex_pi_state *pi_state)
358{
359 if (!atomic_dec_and_test(&pi_state->refcount))
360 return;
361
362 /*
363 * If pi_state->owner is NULL, the owner is most probably dying
364 * and has cleaned up the pi_state already
365 */
366 if (pi_state->owner) {
367 spin_lock_irq(&pi_state->owner->pi_lock);
368 list_del_init(&pi_state->list);
369 spin_unlock_irq(&pi_state->owner->pi_lock);
370
371 rt_mutex_proxy_unlock(&pi_state->pi_mutex, pi_state->owner);
372 }
373
374 if (current->pi_state_cache)
375 kfree(pi_state);
376 else {
377 /*
378 * pi_state->list is already empty.
379 * clear pi_state->owner.
380 * refcount is at 0 - put it back to 1.
381 */
382 pi_state->owner = NULL;
383 atomic_set(&pi_state->refcount, 1);
384 current->pi_state_cache = pi_state;
385 }
386}
387
388/*
389 * Look up the task based on what TID userspace gave us.
390 * We dont trust it.
391 */
392static struct task_struct * futex_find_get_task(pid_t pid)
393{
394 struct task_struct *p;
David Howellsc69e8d92008-11-14 10:39:19 +1100395 const struct cred *cred = current_cred(), *pcred;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700396
Oleg Nesterovd359b542006-09-29 02:00:55 -0700397 rcu_read_lock();
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -0700398 p = find_task_by_vpid(pid);
David Howellsc69e8d92008-11-14 10:39:19 +1100399 if (!p) {
Thomas Gleixnera06381f2007-06-23 11:48:40 +0200400 p = ERR_PTR(-ESRCH);
David Howellsc69e8d92008-11-14 10:39:19 +1100401 } else {
402 pcred = __task_cred(p);
403 if (cred->euid != pcred->euid &&
404 cred->euid != pcred->uid)
405 p = ERR_PTR(-ESRCH);
406 else
407 get_task_struct(p);
408 }
Thomas Gleixnera06381f2007-06-23 11:48:40 +0200409
Oleg Nesterovd359b542006-09-29 02:00:55 -0700410 rcu_read_unlock();
Ingo Molnarc87e2832006-06-27 02:54:58 -0700411
412 return p;
413}
414
415/*
416 * This task is holding PI mutexes at exit time => bad.
417 * Kernel cleans up PI-state, but userspace is likely hosed.
418 * (Robust-futex cleanup is separate and might save the day for userspace.)
419 */
420void exit_pi_state_list(struct task_struct *curr)
421{
Ingo Molnarc87e2832006-06-27 02:54:58 -0700422 struct list_head *next, *head = &curr->pi_state_list;
423 struct futex_pi_state *pi_state;
Ingo Molnar627371d2006-07-29 05:16:20 +0200424 struct futex_hash_bucket *hb;
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200425 union futex_key key = FUTEX_KEY_INIT;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700426
Thomas Gleixnera0c1e902008-02-23 15:23:57 -0800427 if (!futex_cmpxchg_enabled)
428 return;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700429 /*
430 * We are a ZOMBIE and nobody can enqueue itself on
431 * pi_state_list anymore, but we have to be careful
Ingo Molnar627371d2006-07-29 05:16:20 +0200432 * versus waiters unqueueing themselves:
Ingo Molnarc87e2832006-06-27 02:54:58 -0700433 */
434 spin_lock_irq(&curr->pi_lock);
435 while (!list_empty(head)) {
436
437 next = head->next;
438 pi_state = list_entry(next, struct futex_pi_state, list);
439 key = pi_state->key;
Ingo Molnar627371d2006-07-29 05:16:20 +0200440 hb = hash_futex(&key);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700441 spin_unlock_irq(&curr->pi_lock);
442
Ingo Molnarc87e2832006-06-27 02:54:58 -0700443 spin_lock(&hb->lock);
444
445 spin_lock_irq(&curr->pi_lock);
Ingo Molnar627371d2006-07-29 05:16:20 +0200446 /*
447 * We dropped the pi-lock, so re-check whether this
448 * task still owns the PI-state:
449 */
Ingo Molnarc87e2832006-06-27 02:54:58 -0700450 if (head->next != next) {
451 spin_unlock(&hb->lock);
452 continue;
453 }
454
Ingo Molnarc87e2832006-06-27 02:54:58 -0700455 WARN_ON(pi_state->owner != curr);
Ingo Molnar627371d2006-07-29 05:16:20 +0200456 WARN_ON(list_empty(&pi_state->list));
457 list_del_init(&pi_state->list);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700458 pi_state->owner = NULL;
459 spin_unlock_irq(&curr->pi_lock);
460
461 rt_mutex_unlock(&pi_state->pi_mutex);
462
463 spin_unlock(&hb->lock);
464
465 spin_lock_irq(&curr->pi_lock);
466 }
467 spin_unlock_irq(&curr->pi_lock);
468}
469
470static int
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700471lookup_pi_state(u32 uval, struct futex_hash_bucket *hb,
472 union futex_key *key, struct futex_pi_state **ps)
Ingo Molnarc87e2832006-06-27 02:54:58 -0700473{
474 struct futex_pi_state *pi_state = NULL;
475 struct futex_q *this, *next;
Pierre Peifferec92d082007-05-09 02:35:00 -0700476 struct plist_head *head;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700477 struct task_struct *p;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700478 pid_t pid = uval & FUTEX_TID_MASK;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700479
480 head = &hb->chain;
481
Pierre Peifferec92d082007-05-09 02:35:00 -0700482 plist_for_each_entry_safe(this, next, head, list) {
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700483 if (match_futex(&this->key, key)) {
Ingo Molnarc87e2832006-06-27 02:54:58 -0700484 /*
485 * Another waiter already exists - bump up
486 * the refcount and return its pi_state:
487 */
488 pi_state = this->pi_state;
Thomas Gleixner06a9ec22006-07-10 04:44:30 -0700489 /*
490 * Userspace might have messed up non PI and PI futexes
491 */
492 if (unlikely(!pi_state))
493 return -EINVAL;
494
Ingo Molnar627371d2006-07-29 05:16:20 +0200495 WARN_ON(!atomic_read(&pi_state->refcount));
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700496 WARN_ON(pid && pi_state->owner &&
497 pi_state->owner->pid != pid);
Ingo Molnar627371d2006-07-29 05:16:20 +0200498
Ingo Molnarc87e2832006-06-27 02:54:58 -0700499 atomic_inc(&pi_state->refcount);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700500 *ps = pi_state;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700501
502 return 0;
503 }
504 }
505
506 /*
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200507 * We are the first waiter - try to look up the real owner and attach
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700508 * the new pi_state to it, but bail out when TID = 0
Ingo Molnarc87e2832006-06-27 02:54:58 -0700509 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700510 if (!pid)
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200511 return -ESRCH;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700512 p = futex_find_get_task(pid);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700513 if (IS_ERR(p))
514 return PTR_ERR(p);
515
516 /*
517 * We need to look at the task state flags to figure out,
518 * whether the task is exiting. To protect against the do_exit
519 * change of the task flags, we do this protected by
520 * p->pi_lock:
521 */
522 spin_lock_irq(&p->pi_lock);
523 if (unlikely(p->flags & PF_EXITING)) {
524 /*
525 * The task is on the way out. When PF_EXITPIDONE is
526 * set, we know that the task has finished the
527 * cleanup:
528 */
529 int ret = (p->flags & PF_EXITPIDONE) ? -ESRCH : -EAGAIN;
530
531 spin_unlock_irq(&p->pi_lock);
532 put_task_struct(p);
533 return ret;
534 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700535
536 pi_state = alloc_pi_state();
537
538 /*
539 * Initialize the pi_mutex in locked state and make 'p'
540 * the owner of it:
541 */
542 rt_mutex_init_proxy_locked(&pi_state->pi_mutex, p);
543
544 /* Store the key for possible exit cleanups: */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700545 pi_state->key = *key;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700546
Ingo Molnar627371d2006-07-29 05:16:20 +0200547 WARN_ON(!list_empty(&pi_state->list));
Ingo Molnarc87e2832006-06-27 02:54:58 -0700548 list_add(&pi_state->list, &p->pi_state_list);
549 pi_state->owner = p;
550 spin_unlock_irq(&p->pi_lock);
551
552 put_task_struct(p);
553
Pierre Peifferd0aa7a72007-05-09 02:35:02 -0700554 *ps = pi_state;
Ingo Molnarc87e2832006-06-27 02:54:58 -0700555
556 return 0;
557}
558
Darren Hart1a520842009-04-03 13:39:52 -0700559/**
560 * futex_lock_pi_atomic() - atomic work required to acquire a pi aware futex
561 * @uaddr: the pi futex user address
562 * @hb: the pi futex hash bucket
563 * @key: the futex key associated with uaddr and hb
564 * @ps: the pi_state pointer where we store the result of the lookup
565 * @task: the task to perform the atomic lock work for. This will be
566 * "current" except in the case of requeue pi.
567 *
568 * Returns:
569 * 0 - ready to wait
570 * 1 - acquired the lock
571 * <0 - error
572 *
573 * The hb->lock and futex_key refs shall be held by the caller.
574 */
575static int futex_lock_pi_atomic(u32 __user *uaddr, struct futex_hash_bucket *hb,
576 union futex_key *key,
577 struct futex_pi_state **ps,
578 struct task_struct *task)
579{
580 int lock_taken, ret, ownerdied = 0;
581 u32 uval, newval, curval;
582
583retry:
584 ret = lock_taken = 0;
585
586 /*
587 * To avoid races, we attempt to take the lock here again
588 * (by doing a 0 -> TID atomic cmpxchg), while holding all
589 * the locks. It will most likely not succeed.
590 */
591 newval = task_pid_vnr(task);
592
593 curval = cmpxchg_futex_value_locked(uaddr, 0, newval);
594
595 if (unlikely(curval == -EFAULT))
596 return -EFAULT;
597
598 /*
599 * Detect deadlocks.
600 */
601 if ((unlikely((curval & FUTEX_TID_MASK) == task_pid_vnr(task))))
602 return -EDEADLK;
603
604 /*
605 * Surprise - we got the lock. Just return to userspace:
606 */
607 if (unlikely(!curval))
608 return 1;
609
610 uval = curval;
611
612 /*
613 * Set the FUTEX_WAITERS flag, so the owner will know it has someone
614 * to wake at the next unlock.
615 */
616 newval = curval | FUTEX_WAITERS;
617
618 /*
619 * There are two cases, where a futex might have no owner (the
620 * owner TID is 0): OWNER_DIED. We take over the futex in this
621 * case. We also do an unconditional take over, when the owner
622 * of the futex died.
623 *
624 * This is safe as we are protected by the hash bucket lock !
625 */
626 if (unlikely(ownerdied || !(curval & FUTEX_TID_MASK))) {
627 /* Keep the OWNER_DIED bit */
628 newval = (curval & ~FUTEX_TID_MASK) | task_pid_vnr(task);
629 ownerdied = 0;
630 lock_taken = 1;
631 }
632
633 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
634
635 if (unlikely(curval == -EFAULT))
636 return -EFAULT;
637 if (unlikely(curval != uval))
638 goto retry;
639
640 /*
641 * We took the lock due to owner died take over.
642 */
643 if (unlikely(lock_taken))
644 return 1;
645
646 /*
647 * We dont have the lock. Look up the PI state (or create it if
648 * we are the first waiter):
649 */
650 ret = lookup_pi_state(uval, hb, key, ps);
651
652 if (unlikely(ret)) {
653 switch (ret) {
654 case -ESRCH:
655 /*
656 * No owner found for this futex. Check if the
657 * OWNER_DIED bit is set to figure out whether
658 * this is a robust futex or not.
659 */
660 if (get_futex_value_locked(&curval, uaddr))
661 return -EFAULT;
662
663 /*
664 * We simply start over in case of a robust
665 * futex. The code above will take the futex
666 * and return happy.
667 */
668 if (curval & FUTEX_OWNER_DIED) {
669 ownerdied = 1;
670 goto retry;
671 }
672 default:
673 break;
674 }
675 }
676
677 return ret;
678}
679
Ingo Molnarc87e2832006-06-27 02:54:58 -0700680/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700681 * The hash bucket lock must be held when this is called.
682 * Afterwards, the futex_q must not be accessed.
683 */
684static void wake_futex(struct futex_q *q)
685{
Pierre Peifferec92d082007-05-09 02:35:00 -0700686 plist_del(&q->list, &q->list.plist);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700687 /*
688 * The lock in wake_up_all() is a crucial memory barrier after the
Pierre Peifferec92d082007-05-09 02:35:00 -0700689 * plist_del() and also before assigning to q->lock_ptr.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700690 */
Darren Hart73500ac2008-12-17 17:29:56 -0800691 wake_up(&q->waiter);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700692 /*
693 * The waiting task can free the futex_q as soon as this is written,
694 * without taking any locks. This must come last.
Andrew Morton8e311082005-12-23 19:54:46 -0800695 *
Darren Hartb2d09942009-03-12 00:55:37 -0700696 * A memory barrier is required here to prevent the following store to
697 * lock_ptr from getting ahead of the wakeup. Clearing the lock at the
698 * end of wake_up() does not prevent this store from moving.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700699 */
Ralf Baechleccdea2f2006-12-06 20:40:26 -0800700 smp_wmb();
Linus Torvalds1da177e2005-04-16 15:20:36 -0700701 q->lock_ptr = NULL;
702}
703
Ingo Molnarc87e2832006-06-27 02:54:58 -0700704static int wake_futex_pi(u32 __user *uaddr, u32 uval, struct futex_q *this)
705{
706 struct task_struct *new_owner;
707 struct futex_pi_state *pi_state = this->pi_state;
708 u32 curval, newval;
709
710 if (!pi_state)
711 return -EINVAL;
712
Ingo Molnar217788672007-03-16 13:38:31 -0800713 spin_lock(&pi_state->pi_mutex.wait_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700714 new_owner = rt_mutex_next_owner(&pi_state->pi_mutex);
715
716 /*
717 * This happens when we have stolen the lock and the original
718 * pending owner did not enqueue itself back on the rt_mutex.
719 * Thats not a tragedy. We know that way, that a lock waiter
720 * is on the fly. We make the futex_q waiter the pending owner.
721 */
722 if (!new_owner)
723 new_owner = this->task;
724
725 /*
726 * We pass it to the next owner. (The WAITERS bit is always
727 * kept enabled while there is PI state around. We must also
728 * preserve the owner died bit.)
729 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200730 if (!(uval & FUTEX_OWNER_DIED)) {
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700731 int ret = 0;
732
Pavel Emelyanovb4888932007-10-18 23:40:14 -0700733 newval = FUTEX_WAITERS | task_pid_vnr(new_owner);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700734
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700735 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700736
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200737 if (curval == -EFAULT)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700738 ret = -EFAULT;
Thomas Gleixnercde898f2007-12-05 15:46:09 +0100739 else if (curval != uval)
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -0700740 ret = -EINVAL;
741 if (ret) {
742 spin_unlock(&pi_state->pi_mutex.wait_lock);
743 return ret;
744 }
Ingo Molnare3f2dde2006-07-29 05:17:57 +0200745 }
Ingo Molnarc87e2832006-06-27 02:54:58 -0700746
Ingo Molnar627371d2006-07-29 05:16:20 +0200747 spin_lock_irq(&pi_state->owner->pi_lock);
748 WARN_ON(list_empty(&pi_state->list));
749 list_del_init(&pi_state->list);
750 spin_unlock_irq(&pi_state->owner->pi_lock);
751
752 spin_lock_irq(&new_owner->pi_lock);
753 WARN_ON(!list_empty(&pi_state->list));
Ingo Molnarc87e2832006-06-27 02:54:58 -0700754 list_add(&pi_state->list, &new_owner->pi_state_list);
755 pi_state->owner = new_owner;
Ingo Molnar627371d2006-07-29 05:16:20 +0200756 spin_unlock_irq(&new_owner->pi_lock);
757
Ingo Molnar217788672007-03-16 13:38:31 -0800758 spin_unlock(&pi_state->pi_mutex.wait_lock);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700759 rt_mutex_unlock(&pi_state->pi_mutex);
760
761 return 0;
762}
763
764static int unlock_futex_pi(u32 __user *uaddr, u32 uval)
765{
766 u32 oldval;
767
768 /*
769 * There is no waiter, so we unlock the futex. The owner died
770 * bit has not to be preserved here. We are the owner:
771 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -0700772 oldval = cmpxchg_futex_value_locked(uaddr, uval, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -0700773
774 if (oldval == -EFAULT)
775 return oldval;
776 if (oldval != uval)
777 return -EAGAIN;
778
779 return 0;
780}
781
Linus Torvalds1da177e2005-04-16 15:20:36 -0700782/*
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700783 * Express the locking dependencies for lockdep:
784 */
785static inline void
786double_lock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
787{
788 if (hb1 <= hb2) {
789 spin_lock(&hb1->lock);
790 if (hb1 < hb2)
791 spin_lock_nested(&hb2->lock, SINGLE_DEPTH_NESTING);
792 } else { /* hb1 > hb2 */
793 spin_lock(&hb2->lock);
794 spin_lock_nested(&hb1->lock, SINGLE_DEPTH_NESTING);
795 }
796}
797
Darren Hart5eb3dc62009-03-12 00:55:52 -0700798static inline void
799double_unlock_hb(struct futex_hash_bucket *hb1, struct futex_hash_bucket *hb2)
800{
Darren Hartf061d352009-03-12 15:11:18 -0700801 spin_unlock(&hb1->lock);
Ingo Molnar88f502f2009-03-13 10:32:07 +0100802 if (hb1 != hb2)
803 spin_unlock(&hb2->lock);
Darren Hart5eb3dc62009-03-12 00:55:52 -0700804}
805
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700806/*
Darren Hartb2d09942009-03-12 00:55:37 -0700807 * Wake up waiters matching bitset queued on this futex (uaddr).
Linus Torvalds1da177e2005-04-16 15:20:36 -0700808 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200809static int futex_wake(u32 __user *uaddr, int fshared, int nr_wake, u32 bitset)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700810{
Ingo Molnare2970f22006-06-27 02:54:47 -0700811 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700812 struct futex_q *this, *next;
Pierre Peifferec92d082007-05-09 02:35:00 -0700813 struct plist_head *head;
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200814 union futex_key key = FUTEX_KEY_INIT;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700815 int ret;
816
Thomas Gleixnercd689982008-02-01 17:45:14 +0100817 if (!bitset)
818 return -EINVAL;
819
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700820 ret = get_futex_key(uaddr, fshared, &key);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700821 if (unlikely(ret != 0))
822 goto out;
823
Ingo Molnare2970f22006-06-27 02:54:47 -0700824 hb = hash_futex(&key);
825 spin_lock(&hb->lock);
826 head = &hb->chain;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700827
Pierre Peifferec92d082007-05-09 02:35:00 -0700828 plist_for_each_entry_safe(this, next, head, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700829 if (match_futex (&this->key, &key)) {
Ingo Molnared6f7b12006-07-01 04:35:46 -0700830 if (this->pi_state) {
831 ret = -EINVAL;
832 break;
833 }
Thomas Gleixnercd689982008-02-01 17:45:14 +0100834
835 /* Check if one of the bits is set in both bitsets */
836 if (!(this->bitset & bitset))
837 continue;
838
Linus Torvalds1da177e2005-04-16 15:20:36 -0700839 wake_futex(this);
840 if (++ret >= nr_wake)
841 break;
842 }
843 }
844
Ingo Molnare2970f22006-06-27 02:54:47 -0700845 spin_unlock(&hb->lock);
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200846 put_futex_key(fshared, &key);
Darren Hart42d35d42008-12-29 15:49:53 -0800847out:
Linus Torvalds1da177e2005-04-16 15:20:36 -0700848 return ret;
849}
850
851/*
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700852 * Wake up all waiters hashed on the physical page that is mapped
853 * to this virtual address:
854 */
Ingo Molnare2970f22006-06-27 02:54:47 -0700855static int
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200856futex_wake_op(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
Ingo Molnare2970f22006-06-27 02:54:47 -0700857 int nr_wake, int nr_wake2, int op)
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700858{
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200859 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
Ingo Molnare2970f22006-06-27 02:54:47 -0700860 struct futex_hash_bucket *hb1, *hb2;
Pierre Peifferec92d082007-05-09 02:35:00 -0700861 struct plist_head *head;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700862 struct futex_q *this, *next;
Darren Harte4dc5b72009-03-12 00:56:13 -0700863 int ret, op_ret;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700864
Darren Harte4dc5b72009-03-12 00:56:13 -0700865retry:
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700866 ret = get_futex_key(uaddr1, fshared, &key1);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700867 if (unlikely(ret != 0))
868 goto out;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700869 ret = get_futex_key(uaddr2, fshared, &key2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700870 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -0800871 goto out_put_key1;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700872
Ingo Molnare2970f22006-06-27 02:54:47 -0700873 hb1 = hash_futex(&key1);
874 hb2 = hash_futex(&key2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700875
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700876 double_lock_hb(hb1, hb2);
Darren Harte4dc5b72009-03-12 00:56:13 -0700877retry_private:
Ingo Molnare2970f22006-06-27 02:54:47 -0700878 op_ret = futex_atomic_op_inuser(op, uaddr2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700879 if (unlikely(op_ret < 0)) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700880 u32 dummy;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700881
Darren Hart5eb3dc62009-03-12 00:55:52 -0700882 double_unlock_hb(hb1, hb2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700883
David Howells7ee1dd32006-01-06 00:11:44 -0800884#ifndef CONFIG_MMU
Ingo Molnare2970f22006-06-27 02:54:47 -0700885 /*
886 * we don't get EFAULT from MMU faults if we don't have an MMU,
887 * but we might get them from range checking
888 */
David Howells7ee1dd32006-01-06 00:11:44 -0800889 ret = op_ret;
Darren Hart42d35d42008-12-29 15:49:53 -0800890 goto out_put_keys;
David Howells7ee1dd32006-01-06 00:11:44 -0800891#endif
892
David Gibson796f8d92005-11-07 00:59:33 -0800893 if (unlikely(op_ret != -EFAULT)) {
894 ret = op_ret;
Darren Hart42d35d42008-12-29 15:49:53 -0800895 goto out_put_keys;
David Gibson796f8d92005-11-07 00:59:33 -0800896 }
897
Ingo Molnare2970f22006-06-27 02:54:47 -0700898 ret = get_user(dummy, uaddr2);
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700899 if (ret)
Darren Hartde87fcc2009-03-12 00:55:46 -0700900 goto out_put_keys;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700901
Darren Harte4dc5b72009-03-12 00:56:13 -0700902 if (!fshared)
903 goto retry_private;
904
Darren Hartde87fcc2009-03-12 00:55:46 -0700905 put_futex_key(fshared, &key2);
906 put_futex_key(fshared, &key1);
Darren Harte4dc5b72009-03-12 00:56:13 -0700907 goto retry;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700908 }
909
Ingo Molnare2970f22006-06-27 02:54:47 -0700910 head = &hb1->chain;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700911
Pierre Peifferec92d082007-05-09 02:35:00 -0700912 plist_for_each_entry_safe(this, next, head, list) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700913 if (match_futex (&this->key, &key1)) {
914 wake_futex(this);
915 if (++ret >= nr_wake)
916 break;
917 }
918 }
919
920 if (op_ret > 0) {
Ingo Molnare2970f22006-06-27 02:54:47 -0700921 head = &hb2->chain;
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700922
923 op_ret = 0;
Pierre Peifferec92d082007-05-09 02:35:00 -0700924 plist_for_each_entry_safe(this, next, head, list) {
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700925 if (match_futex (&this->key, &key2)) {
926 wake_futex(this);
927 if (++op_ret >= nr_wake2)
928 break;
929 }
930 }
931 ret += op_ret;
932 }
933
Darren Hart5eb3dc62009-03-12 00:55:52 -0700934 double_unlock_hb(hb1, hb2);
Darren Hart42d35d42008-12-29 15:49:53 -0800935out_put_keys:
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200936 put_futex_key(fshared, &key2);
Darren Hart42d35d42008-12-29 15:49:53 -0800937out_put_key1:
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200938 put_futex_key(fshared, &key1);
Darren Hart42d35d42008-12-29 15:49:53 -0800939out:
Jakub Jelinek4732efb2005-09-06 15:16:25 -0700940 return ret;
941}
942
943/*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700944 * Requeue all waiters hashed on one physical page to another
945 * physical page.
946 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +0200947static int futex_requeue(u32 __user *uaddr1, int fshared, u32 __user *uaddr2,
Ingo Molnare2970f22006-06-27 02:54:47 -0700948 int nr_wake, int nr_requeue, u32 *cmpval)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700949{
Peter Zijlstra38d47c12008-09-26 19:32:20 +0200950 union futex_key key1 = FUTEX_KEY_INIT, key2 = FUTEX_KEY_INIT;
Ingo Molnare2970f22006-06-27 02:54:47 -0700951 struct futex_hash_bucket *hb1, *hb2;
Pierre Peifferec92d082007-05-09 02:35:00 -0700952 struct plist_head *head1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700953 struct futex_q *this, *next;
954 int ret, drop_count = 0;
955
Darren Hart42d35d42008-12-29 15:49:53 -0800956retry:
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700957 ret = get_futex_key(uaddr1, fshared, &key1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700958 if (unlikely(ret != 0))
959 goto out;
Eric Dumazet34f01cc2007-05-09 02:35:04 -0700960 ret = get_futex_key(uaddr2, fshared, &key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700961 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -0800962 goto out_put_key1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700963
Ingo Molnare2970f22006-06-27 02:54:47 -0700964 hb1 = hash_futex(&key1);
965 hb2 = hash_futex(&key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700966
Darren Harte4dc5b72009-03-12 00:56:13 -0700967retry_private:
Ingo Molnar8b8f3192006-07-03 00:25:05 -0700968 double_lock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700969
Ingo Molnare2970f22006-06-27 02:54:47 -0700970 if (likely(cmpval != NULL)) {
971 u32 curval;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700972
Ingo Molnare2970f22006-06-27 02:54:47 -0700973 ret = get_futex_value_locked(&curval, uaddr1);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700974
975 if (unlikely(ret)) {
Darren Hart5eb3dc62009-03-12 00:55:52 -0700976 double_unlock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700977
Darren Harte4dc5b72009-03-12 00:56:13 -0700978 ret = get_user(curval, uaddr1);
979 if (ret)
980 goto out_put_keys;
981
982 if (!fshared)
983 goto retry_private;
984
Darren Hartde87fcc2009-03-12 00:55:46 -0700985 put_futex_key(fshared, &key2);
986 put_futex_key(fshared, &key1);
Darren Harte4dc5b72009-03-12 00:56:13 -0700987 goto retry;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700988 }
Ingo Molnare2970f22006-06-27 02:54:47 -0700989 if (curval != *cmpval) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700990 ret = -EAGAIN;
991 goto out_unlock;
992 }
993 }
994
Ingo Molnare2970f22006-06-27 02:54:47 -0700995 head1 = &hb1->chain;
Pierre Peifferec92d082007-05-09 02:35:00 -0700996 plist_for_each_entry_safe(this, next, head1, list) {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700997 if (!match_futex (&this->key, &key1))
998 continue;
999 if (++ret <= nr_wake) {
1000 wake_futex(this);
1001 } else {
Sebastien Dugue59e0e0a2006-06-27 02:55:03 -07001002 /*
1003 * If key1 and key2 hash to the same bucket, no need to
1004 * requeue.
1005 */
1006 if (likely(head1 != &hb2->chain)) {
Pierre Peifferec92d082007-05-09 02:35:00 -07001007 plist_del(&this->list, &hb1->chain);
1008 plist_add(&this->list, &hb2->chain);
Sebastien Dugue59e0e0a2006-06-27 02:55:03 -07001009 this->lock_ptr = &hb2->lock;
Pierre Peifferec92d082007-05-09 02:35:00 -07001010#ifdef CONFIG_DEBUG_PI_LIST
1011 this->list.plist.lock = &hb2->lock;
1012#endif
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001013 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001014 this->key = key2;
Rusty Russell9adef582007-05-08 00:26:42 -07001015 get_futex_key_refs(&key2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001016 drop_count++;
1017
1018 if (ret - nr_wake >= nr_requeue)
1019 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001020 }
1021 }
1022
1023out_unlock:
Darren Hart5eb3dc62009-03-12 00:55:52 -07001024 double_unlock_hb(hb1, hb2);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001025
Rusty Russell9adef582007-05-08 00:26:42 -07001026 /* drop_futex_key_refs() must be called outside the spinlocks. */
Linus Torvalds1da177e2005-04-16 15:20:36 -07001027 while (--drop_count >= 0)
Rusty Russell9adef582007-05-08 00:26:42 -07001028 drop_futex_key_refs(&key1);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001029
Darren Hart42d35d42008-12-29 15:49:53 -08001030out_put_keys:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001031 put_futex_key(fshared, &key2);
Darren Hart42d35d42008-12-29 15:49:53 -08001032out_put_key1:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001033 put_futex_key(fshared, &key1);
Darren Hart42d35d42008-12-29 15:49:53 -08001034out:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001035 return ret;
1036}
1037
1038/* The key must be already stored in q->key. */
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001039static inline struct futex_hash_bucket *queue_lock(struct futex_q *q)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001040{
Ingo Molnare2970f22006-06-27 02:54:47 -07001041 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001042
Darren Hart73500ac2008-12-17 17:29:56 -08001043 init_waitqueue_head(&q->waiter);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001044
Rusty Russell9adef582007-05-08 00:26:42 -07001045 get_futex_key_refs(&q->key);
Ingo Molnare2970f22006-06-27 02:54:47 -07001046 hb = hash_futex(&q->key);
1047 q->lock_ptr = &hb->lock;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001048
Ingo Molnare2970f22006-06-27 02:54:47 -07001049 spin_lock(&hb->lock);
1050 return hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001051}
1052
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001053static inline void queue_me(struct futex_q *q, struct futex_hash_bucket *hb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001054{
Pierre Peifferec92d082007-05-09 02:35:00 -07001055 int prio;
1056
1057 /*
1058 * The priority used to register this element is
1059 * - either the real thread-priority for the real-time threads
1060 * (i.e. threads with a priority lower than MAX_RT_PRIO)
1061 * - or MAX_RT_PRIO for non-RT threads.
1062 * Thus, all RT-threads are woken first in priority order, and
1063 * the others are woken last, in FIFO order.
1064 */
1065 prio = min(current->normal_prio, MAX_RT_PRIO);
1066
1067 plist_node_init(&q->list, prio);
1068#ifdef CONFIG_DEBUG_PI_LIST
1069 q->list.plist.lock = &hb->lock;
1070#endif
1071 plist_add(&q->list, &hb->chain);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001072 q->task = current;
Ingo Molnare2970f22006-06-27 02:54:47 -07001073 spin_unlock(&hb->lock);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001074}
1075
1076static inline void
Ingo Molnare2970f22006-06-27 02:54:47 -07001077queue_unlock(struct futex_q *q, struct futex_hash_bucket *hb)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001078{
Ingo Molnare2970f22006-06-27 02:54:47 -07001079 spin_unlock(&hb->lock);
Rusty Russell9adef582007-05-08 00:26:42 -07001080 drop_futex_key_refs(&q->key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001081}
1082
1083/*
1084 * queue_me and unqueue_me must be called as a pair, each
1085 * exactly once. They are called with the hashed spinlock held.
1086 */
1087
Linus Torvalds1da177e2005-04-16 15:20:36 -07001088/* Return 1 if we were still queued (ie. 0 means we were woken) */
1089static int unqueue_me(struct futex_q *q)
1090{
Linus Torvalds1da177e2005-04-16 15:20:36 -07001091 spinlock_t *lock_ptr;
Ingo Molnare2970f22006-06-27 02:54:47 -07001092 int ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001093
1094 /* In the common case we don't take the spinlock, which is nice. */
Darren Hart42d35d42008-12-29 15:49:53 -08001095retry:
Linus Torvalds1da177e2005-04-16 15:20:36 -07001096 lock_ptr = q->lock_ptr;
Christian Borntraegere91467e2006-08-05 12:13:52 -07001097 barrier();
Stephen Hemmingerc80544d2007-10-18 03:07:05 -07001098 if (lock_ptr != NULL) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001099 spin_lock(lock_ptr);
1100 /*
1101 * q->lock_ptr can change between reading it and
1102 * spin_lock(), causing us to take the wrong lock. This
1103 * corrects the race condition.
1104 *
1105 * Reasoning goes like this: if we have the wrong lock,
1106 * q->lock_ptr must have changed (maybe several times)
1107 * between reading it and the spin_lock(). It can
1108 * change again after the spin_lock() but only if it was
1109 * already changed before the spin_lock(). It cannot,
1110 * however, change back to the original value. Therefore
1111 * we can detect whether we acquired the correct lock.
1112 */
1113 if (unlikely(lock_ptr != q->lock_ptr)) {
1114 spin_unlock(lock_ptr);
1115 goto retry;
1116 }
Pierre Peifferec92d082007-05-09 02:35:00 -07001117 WARN_ON(plist_node_empty(&q->list));
1118 plist_del(&q->list, &q->list.plist);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001119
1120 BUG_ON(q->pi_state);
1121
Linus Torvalds1da177e2005-04-16 15:20:36 -07001122 spin_unlock(lock_ptr);
1123 ret = 1;
1124 }
1125
Rusty Russell9adef582007-05-08 00:26:42 -07001126 drop_futex_key_refs(&q->key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001127 return ret;
1128}
1129
Ingo Molnarc87e2832006-06-27 02:54:58 -07001130/*
1131 * PI futexes can not be requeued and must remove themself from the
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001132 * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
1133 * and dropped here.
Ingo Molnarc87e2832006-06-27 02:54:58 -07001134 */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001135static void unqueue_me_pi(struct futex_q *q)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001136{
Pierre Peifferec92d082007-05-09 02:35:00 -07001137 WARN_ON(plist_node_empty(&q->list));
1138 plist_del(&q->list, &q->list.plist);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001139
1140 BUG_ON(!q->pi_state);
1141 free_pi_state(q->pi_state);
1142 q->pi_state = NULL;
1143
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001144 spin_unlock(q->lock_ptr);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001145
Rusty Russell9adef582007-05-08 00:26:42 -07001146 drop_futex_key_refs(&q->key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001147}
1148
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001149/*
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001150 * Fixup the pi_state owner with the new owner.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001151 *
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001152 * Must be called with hash bucket lock held and mm->sem held for non
1153 * private futexes.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001154 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001155static int fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001156 struct task_struct *newowner, int fshared)
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001157{
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001158 u32 newtid = task_pid_vnr(newowner) | FUTEX_WAITERS;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001159 struct futex_pi_state *pi_state = q->pi_state;
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001160 struct task_struct *oldowner = pi_state->owner;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001161 u32 uval, curval, newval;
Darren Harte4dc5b72009-03-12 00:56:13 -07001162 int ret;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001163
1164 /* Owner died? */
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001165 if (!pi_state->owner)
1166 newtid |= FUTEX_OWNER_DIED;
1167
1168 /*
1169 * We are here either because we stole the rtmutex from the
1170 * pending owner or we are the pending owner which failed to
1171 * get the rtmutex. We have to replace the pending owner TID
1172 * in the user space variable. This must be atomic as we have
1173 * to preserve the owner died bit here.
1174 *
Darren Hartb2d09942009-03-12 00:55:37 -07001175 * Note: We write the user space value _before_ changing the pi_state
1176 * because we can fault here. Imagine swapped out pages or a fork
1177 * that marked all the anonymous memory readonly for cow.
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001178 *
1179 * Modifying pi_state _before_ the user space value would
1180 * leave the pi_state in an inconsistent state when we fault
1181 * here, because we need to drop the hash bucket lock to
1182 * handle the fault. This might be observed in the PID check
1183 * in lookup_pi_state.
1184 */
1185retry:
1186 if (get_futex_value_locked(&uval, uaddr))
1187 goto handle_fault;
1188
1189 while (1) {
1190 newval = (uval & FUTEX_OWNER_DIED) | newtid;
1191
1192 curval = cmpxchg_futex_value_locked(uaddr, uval, newval);
1193
1194 if (curval == -EFAULT)
1195 goto handle_fault;
1196 if (curval == uval)
1197 break;
1198 uval = curval;
1199 }
1200
1201 /*
1202 * We fixed up user space. Now we need to fix the pi_state
1203 * itself.
1204 */
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001205 if (pi_state->owner != NULL) {
1206 spin_lock_irq(&pi_state->owner->pi_lock);
1207 WARN_ON(list_empty(&pi_state->list));
1208 list_del_init(&pi_state->list);
1209 spin_unlock_irq(&pi_state->owner->pi_lock);
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001210 }
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001211
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001212 pi_state->owner = newowner;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001213
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001214 spin_lock_irq(&newowner->pi_lock);
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001215 WARN_ON(!list_empty(&pi_state->list));
Thomas Gleixnercdf71a12008-01-08 19:47:38 +01001216 list_add(&pi_state->list, &newowner->pi_state_list);
1217 spin_unlock_irq(&newowner->pi_lock);
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001218 return 0;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001219
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001220 /*
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001221 * To handle the page fault we need to drop the hash bucket
1222 * lock here. That gives the other task (either the pending
1223 * owner itself or the task which stole the rtmutex) the
1224 * chance to try the fixup of the pi_state. So once we are
1225 * back from handling the fault we need to check the pi_state
1226 * after reacquiring the hash bucket lock and before trying to
1227 * do another fixup. When the fixup has been done already we
1228 * simply return.
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001229 */
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001230handle_fault:
1231 spin_unlock(q->lock_ptr);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001232
Darren Harte4dc5b72009-03-12 00:56:13 -07001233 ret = get_user(uval, uaddr);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001234
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001235 spin_lock(q->lock_ptr);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001236
Thomas Gleixner1b7558e2008-06-23 11:21:58 +02001237 /*
1238 * Check if someone else fixed it for us:
1239 */
1240 if (pi_state->owner != oldowner)
1241 return 0;
1242
1243 if (ret)
1244 return ret;
1245
1246 goto retry;
Pierre Peifferd0aa7a72007-05-09 02:35:02 -07001247}
1248
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001249/*
1250 * In case we must use restart_block to restart a futex_wait,
Steven Rostedtce6bd422007-12-05 15:46:09 +01001251 * we encode in the 'flags' shared capability
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001252 */
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001253#define FLAGS_SHARED 0x01
1254#define FLAGS_CLOCKRT 0x02
Darren Harta72188d2009-04-03 13:40:22 -07001255#define FLAGS_HAS_TIMEOUT 0x04
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001256
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001257static long futex_wait_restart(struct restart_block *restart);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001258
Darren Hartca5f9522009-04-03 13:39:33 -07001259/**
Darren Hartdd973992009-04-03 13:40:02 -07001260 * fixup_owner() - Post lock pi_state and corner case management
1261 * @uaddr: user address of the futex
1262 * @fshared: whether the futex is shared (1) or not (0)
1263 * @q: futex_q (contains pi_state and access to the rt_mutex)
1264 * @locked: if the attempt to take the rt_mutex succeeded (1) or not (0)
1265 *
1266 * After attempting to lock an rt_mutex, this function is called to cleanup
1267 * the pi_state owner as well as handle race conditions that may allow us to
1268 * acquire the lock. Must be called with the hb lock held.
1269 *
1270 * Returns:
1271 * 1 - success, lock taken
1272 * 0 - success, lock not taken
1273 * <0 - on error (-EFAULT)
1274 */
1275static int fixup_owner(u32 __user *uaddr, int fshared, struct futex_q *q,
1276 int locked)
1277{
1278 struct task_struct *owner;
1279 int ret = 0;
1280
1281 if (locked) {
1282 /*
1283 * Got the lock. We might not be the anticipated owner if we
1284 * did a lock-steal - fix up the PI-state in that case:
1285 */
1286 if (q->pi_state->owner != current)
1287 ret = fixup_pi_state_owner(uaddr, q, current, fshared);
1288 goto out;
1289 }
1290
1291 /*
1292 * Catch the rare case, where the lock was released when we were on the
1293 * way back before we locked the hash bucket.
1294 */
1295 if (q->pi_state->owner == current) {
1296 /*
1297 * Try to get the rt_mutex now. This might fail as some other
1298 * task acquired the rt_mutex after we removed ourself from the
1299 * rt_mutex waiters list.
1300 */
1301 if (rt_mutex_trylock(&q->pi_state->pi_mutex)) {
1302 locked = 1;
1303 goto out;
1304 }
1305
1306 /*
1307 * pi_state is incorrect, some other task did a lock steal and
1308 * we returned due to timeout or signal without taking the
1309 * rt_mutex. Too late. We can access the rt_mutex_owner without
1310 * locking, as the other task is now blocked on the hash bucket
1311 * lock. Fix the state up.
1312 */
1313 owner = rt_mutex_owner(&q->pi_state->pi_mutex);
1314 ret = fixup_pi_state_owner(uaddr, q, owner, fshared);
1315 goto out;
1316 }
1317
1318 /*
1319 * Paranoia check. If we did not take the lock, then we should not be
1320 * the owner, nor the pending owner, of the rt_mutex.
1321 */
1322 if (rt_mutex_owner(&q->pi_state->pi_mutex) == current)
1323 printk(KERN_ERR "fixup_owner: ret = %d pi-mutex: %p "
1324 "pi-state %p\n", ret,
1325 q->pi_state->pi_mutex.owner,
1326 q->pi_state->owner);
1327
1328out:
1329 return ret ? ret : locked;
1330}
1331
1332/**
Darren Hartca5f9522009-04-03 13:39:33 -07001333 * futex_wait_queue_me() - queue_me() and wait for wakeup, timeout, or signal
1334 * @hb: the futex hash bucket, must be locked by the caller
1335 * @q: the futex_q to queue up on
1336 * @timeout: the prepared hrtimer_sleeper, or null for no timeout
1337 * @wait: the wait_queue to add to the futex_q after queueing in the hb
1338 */
1339static void futex_wait_queue_me(struct futex_hash_bucket *hb, struct futex_q *q,
1340 struct hrtimer_sleeper *timeout,
1341 wait_queue_t *wait)
1342{
1343 queue_me(q, hb);
1344
1345 /*
1346 * There might have been scheduling since the queue_me(), as we
1347 * cannot hold a spinlock across the get_user() in case it
1348 * faults, and we cannot just set TASK_INTERRUPTIBLE state when
1349 * queueing ourselves into the futex hash. This code thus has to
1350 * rely on the futex_wake() code removing us from hash when it
1351 * wakes us up.
1352 */
1353
1354 /* add_wait_queue is the barrier after __set_current_state. */
1355 __set_current_state(TASK_INTERRUPTIBLE);
1356
1357 /*
1358 * Add current as the futex_q waiter. We don't remove ourselves from
1359 * the wait_queue because we are the only user of it.
1360 */
1361 add_wait_queue(&q->waiter, wait);
1362
1363 /* Arm the timer */
1364 if (timeout) {
1365 hrtimer_start_expires(&timeout->timer, HRTIMER_MODE_ABS);
1366 if (!hrtimer_active(&timeout->timer))
1367 timeout->task = NULL;
1368 }
1369
1370 /*
1371 * !plist_node_empty() is safe here without any lock.
1372 * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
1373 */
1374 if (likely(!plist_node_empty(&q->list))) {
1375 /*
1376 * If the timer has already expired, current will already be
1377 * flagged for rescheduling. Only call schedule if there
1378 * is no timeout, or if it has yet to expire.
1379 */
1380 if (!timeout || timeout->task)
1381 schedule();
1382 }
1383 __set_current_state(TASK_RUNNING);
1384}
1385
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001386static int futex_wait(u32 __user *uaddr, int fshared,
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001387 u32 val, ktime_t *abs_time, u32 bitset, int clockrt)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001388{
Darren Hartca5f9522009-04-03 13:39:33 -07001389 struct hrtimer_sleeper timeout, *to = NULL;
1390 DECLARE_WAITQUEUE(wait, current);
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001391 struct restart_block *restart;
Ingo Molnare2970f22006-06-27 02:54:47 -07001392 struct futex_hash_bucket *hb;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001393 struct futex_q q;
Ingo Molnare2970f22006-06-27 02:54:47 -07001394 u32 uval;
1395 int ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001396
Thomas Gleixnercd689982008-02-01 17:45:14 +01001397 if (!bitset)
1398 return -EINVAL;
1399
Ingo Molnarc87e2832006-06-27 02:54:58 -07001400 q.pi_state = NULL;
Thomas Gleixnercd689982008-02-01 17:45:14 +01001401 q.bitset = bitset;
Darren Hartca5f9522009-04-03 13:39:33 -07001402
1403 if (abs_time) {
1404 to = &timeout;
1405
1406 hrtimer_init_on_stack(&to->timer, clockrt ? CLOCK_REALTIME :
1407 CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1408 hrtimer_init_sleeper(to, current);
1409 hrtimer_set_expires_range_ns(&to->timer, *abs_time,
1410 current->timer_slack_ns);
1411 }
1412
Darren Hart42d35d42008-12-29 15:49:53 -08001413retry:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001414 q.key = FUTEX_KEY_INIT;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001415 ret = get_futex_key(uaddr, fshared, &q.key);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001416 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -08001417 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001418
Darren Harte4dc5b72009-03-12 00:56:13 -07001419retry_private:
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001420 hb = queue_lock(&q);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001421
1422 /*
Darren Hartb2d09942009-03-12 00:55:37 -07001423 * Access the page AFTER the hash-bucket is locked.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001424 * Order is important:
1425 *
1426 * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
1427 * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
1428 *
1429 * The basic logical guarantee of a futex is that it blocks ONLY
1430 * if cond(var) is known to be true at the time of blocking, for
1431 * any cond. If we queued after testing *uaddr, that would open
1432 * a race condition where we could block indefinitely with
1433 * cond(var) false, which would violate the guarantee.
1434 *
1435 * A consequence is that futex_wait() can return zero and absorb
1436 * a wakeup when *uaddr != val on entry to the syscall. This is
1437 * rare, but normal.
1438 *
Darren Hartb2d09942009-03-12 00:55:37 -07001439 * For shared futexes, we hold the mmap semaphore, so the mapping
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001440 * cannot have changed since we looked it up in get_futex_key.
Linus Torvalds1da177e2005-04-16 15:20:36 -07001441 */
Ingo Molnare2970f22006-06-27 02:54:47 -07001442 ret = get_futex_value_locked(&uval, uaddr);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001443
1444 if (unlikely(ret)) {
Ingo Molnare2970f22006-06-27 02:54:47 -07001445 queue_unlock(&q, hb);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001446
Ingo Molnare2970f22006-06-27 02:54:47 -07001447 ret = get_user(uval, uaddr);
Darren Harte4dc5b72009-03-12 00:56:13 -07001448 if (ret)
1449 goto out_put_key;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001450
Darren Harte4dc5b72009-03-12 00:56:13 -07001451 if (!fshared)
1452 goto retry_private;
1453
1454 put_futex_key(fshared, &q.key);
1455 goto retry;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001456 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001457 ret = -EWOULDBLOCK;
Darren Hartca5f9522009-04-03 13:39:33 -07001458
1459 /* Only actually queue if *uaddr contained val. */
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001460 if (unlikely(uval != val)) {
1461 queue_unlock(&q, hb);
1462 goto out_put_key;
1463 }
Linus Torvalds1da177e2005-04-16 15:20:36 -07001464
Darren Hartca5f9522009-04-03 13:39:33 -07001465 /* queue_me and wait for wakeup, timeout, or a signal. */
1466 futex_wait_queue_me(hb, &q, to, &wait);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001467
1468 /* If we were woken (and unqueued), we succeeded, whatever. */
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001469 ret = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001470 if (!unqueue_me(&q))
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001471 goto out_put_key;
1472 ret = -ETIMEDOUT;
Darren Hartca5f9522009-04-03 13:39:33 -07001473 if (to && !to->task)
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001474 goto out_put_key;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001475
Ingo Molnare2970f22006-06-27 02:54:47 -07001476 /*
1477 * We expect signal_pending(current), but another thread may
1478 * have handled it for us already.
1479 */
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001480 ret = -ERESTARTSYS;
Pierre Peifferc19384b2007-05-09 02:35:02 -07001481 if (!abs_time)
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001482 goto out_put_key;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001483
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001484 restart = &current_thread_info()->restart_block;
1485 restart->fn = futex_wait_restart;
1486 restart->futex.uaddr = (u32 *)uaddr;
1487 restart->futex.val = val;
1488 restart->futex.time = abs_time->tv64;
1489 restart->futex.bitset = bitset;
Darren Harta72188d2009-04-03 13:40:22 -07001490 restart->futex.flags = FLAGS_HAS_TIMEOUT;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001491
Peter Zijlstra2fff78c2009-02-11 18:10:10 +01001492 if (fshared)
1493 restart->futex.flags |= FLAGS_SHARED;
1494 if (clockrt)
1495 restart->futex.flags |= FLAGS_CLOCKRT;
1496
1497 ret = -ERESTART_RESTARTBLOCK;
1498
1499out_put_key:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001500 put_futex_key(fshared, &q.key);
Darren Hart42d35d42008-12-29 15:49:53 -08001501out:
Darren Hartca5f9522009-04-03 13:39:33 -07001502 if (to) {
1503 hrtimer_cancel(&to->timer);
1504 destroy_hrtimer_on_stack(&to->timer);
1505 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001506 return ret;
1507}
1508
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001509
1510static long futex_wait_restart(struct restart_block *restart)
1511{
Steven Rostedtce6bd422007-12-05 15:46:09 +01001512 u32 __user *uaddr = (u32 __user *)restart->futex.uaddr;
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001513 int fshared = 0;
Darren Harta72188d2009-04-03 13:40:22 -07001514 ktime_t t, *tp = NULL;
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001515
Darren Harta72188d2009-04-03 13:40:22 -07001516 if (restart->futex.flags & FLAGS_HAS_TIMEOUT) {
1517 t.tv64 = restart->futex.time;
1518 tp = &t;
1519 }
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001520 restart->fn = do_no_restart_syscall;
Steven Rostedtce6bd422007-12-05 15:46:09 +01001521 if (restart->futex.flags & FLAGS_SHARED)
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001522 fshared = 1;
Darren Harta72188d2009-04-03 13:40:22 -07001523 return (long)futex_wait(uaddr, fshared, restart->futex.val, tp,
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001524 restart->futex.bitset,
1525 restart->futex.flags & FLAGS_CLOCKRT);
Nick Piggin72c1bbf2007-05-08 00:26:43 -07001526}
1527
1528
Ingo Molnarc87e2832006-06-27 02:54:58 -07001529/*
1530 * Userspace tried a 0 -> TID atomic transition of the futex value
1531 * and failed. The kernel side here does the whole locking operation:
1532 * if there are waiters then it will block, it does PI, etc. (Due to
1533 * races the kernel might see a 0 value of the futex too.)
1534 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001535static int futex_lock_pi(u32 __user *uaddr, int fshared,
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001536 int detect, ktime_t *time, int trylock)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001537{
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001538 struct hrtimer_sleeper timeout, *to = NULL;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001539 struct futex_hash_bucket *hb;
Darren Hart1a520842009-04-03 13:39:52 -07001540 u32 uval;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001541 struct futex_q q;
Darren Hartdd973992009-04-03 13:40:02 -07001542 int res, ret;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001543
1544 if (refill_pi_state_cache())
1545 return -ENOMEM;
1546
Pierre Peifferc19384b2007-05-09 02:35:02 -07001547 if (time) {
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001548 to = &timeout;
Thomas Gleixner237fc6e2008-04-30 00:55:04 -07001549 hrtimer_init_on_stack(&to->timer, CLOCK_REALTIME,
1550 HRTIMER_MODE_ABS);
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001551 hrtimer_init_sleeper(to, current);
Arjan van de Vencc584b22008-09-01 15:02:30 -07001552 hrtimer_set_expires(&to->timer, *time);
Thomas Gleixnerc5780e92006-09-08 09:47:15 -07001553 }
1554
Ingo Molnarc87e2832006-06-27 02:54:58 -07001555 q.pi_state = NULL;
Darren Hart42d35d42008-12-29 15:49:53 -08001556retry:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001557 q.key = FUTEX_KEY_INIT;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001558 ret = get_futex_key(uaddr, fshared, &q.key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001559 if (unlikely(ret != 0))
Darren Hart42d35d42008-12-29 15:49:53 -08001560 goto out;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001561
Darren Harte4dc5b72009-03-12 00:56:13 -07001562retry_private:
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001563 hb = queue_lock(&q);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001564
Darren Hart1a520842009-04-03 13:39:52 -07001565 ret = futex_lock_pi_atomic(uaddr, hb, &q.key, &q.pi_state, current);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001566 if (unlikely(ret)) {
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001567 switch (ret) {
Darren Hart1a520842009-04-03 13:39:52 -07001568 case 1:
1569 /* We got the lock. */
1570 ret = 0;
1571 goto out_unlock_put_key;
1572 case -EFAULT:
1573 goto uaddr_faulted;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001574 case -EAGAIN:
1575 /*
1576 * Task is exiting and we just wait for the
1577 * exit to complete.
1578 */
1579 queue_unlock(&q, hb);
Darren Hartde87fcc2009-03-12 00:55:46 -07001580 put_futex_key(fshared, &q.key);
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001581 cond_resched();
1582 goto retry;
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001583 default:
Darren Hart42d35d42008-12-29 15:49:53 -08001584 goto out_unlock_put_key;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001585 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001586 }
1587
1588 /*
1589 * Only actually queue now that the atomic ops are done:
1590 */
Eric Sesterhenn82af7ac2008-01-25 10:40:46 +01001591 queue_me(&q, hb);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001592
Ingo Molnarc87e2832006-06-27 02:54:58 -07001593 WARN_ON(!q.pi_state);
1594 /*
1595 * Block on the PI mutex:
1596 */
1597 if (!trylock)
1598 ret = rt_mutex_timed_lock(&q.pi_state->pi_mutex, to, 1);
1599 else {
1600 ret = rt_mutex_trylock(&q.pi_state->pi_mutex);
1601 /* Fixup the trylock return value: */
1602 ret = ret ? 0 : -EWOULDBLOCK;
1603 }
1604
Vernon Mauerya99e4e42006-07-01 04:35:42 -07001605 spin_lock(q.lock_ptr);
Darren Hartdd973992009-04-03 13:40:02 -07001606 /*
1607 * Fixup the pi_state owner and possibly acquire the lock if we
1608 * haven't already.
1609 */
1610 res = fixup_owner(uaddr, fshared, &q, !ret);
1611 /*
1612 * If fixup_owner() returned an error, proprogate that. If it acquired
1613 * the lock, clear our -ETIMEDOUT or -EINTR.
1614 */
1615 if (res)
1616 ret = (res < 0) ? res : 0;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001617
Darren Harte8f63862009-03-12 00:56:06 -07001618 /*
Darren Hartdd973992009-04-03 13:40:02 -07001619 * If fixup_owner() faulted and was unable to handle the fault, unlock
1620 * it and return the fault to userspace.
Darren Harte8f63862009-03-12 00:56:06 -07001621 */
1622 if (ret && (rt_mutex_owner(&q.pi_state->pi_mutex) == current))
1623 rt_mutex_unlock(&q.pi_state->pi_mutex);
1624
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001625 /* Unqueue and drop the lock */
1626 unqueue_me_pi(&q);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001627
Darren Hartdd973992009-04-03 13:40:02 -07001628 goto out;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001629
Darren Hart42d35d42008-12-29 15:49:53 -08001630out_unlock_put_key:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001631 queue_unlock(&q, hb);
1632
Darren Hart42d35d42008-12-29 15:49:53 -08001633out_put_key:
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001634 put_futex_key(fshared, &q.key);
Darren Hart42d35d42008-12-29 15:49:53 -08001635out:
Thomas Gleixner237fc6e2008-04-30 00:55:04 -07001636 if (to)
1637 destroy_hrtimer_on_stack(&to->timer);
Darren Hartdd973992009-04-03 13:40:02 -07001638 return ret != -EINTR ? ret : -ERESTARTNOINTR;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001639
Darren Hart42d35d42008-12-29 15:49:53 -08001640uaddr_faulted:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001641 /*
Darren Hartb5686362008-12-18 15:06:34 -08001642 * We have to r/w *(int __user *)uaddr, and we have to modify it
1643 * atomically. Therefore, if we continue to fault after get_user()
1644 * below, we need to handle the fault ourselves, while still holding
1645 * the mmap_sem. This can occur if the uaddr is under contention as
1646 * we have to drop the mmap_sem in order to call get_user().
Ingo Molnarc87e2832006-06-27 02:54:58 -07001647 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001648 queue_unlock(&q, hb);
1649
Ingo Molnarc87e2832006-06-27 02:54:58 -07001650 ret = get_user(uval, uaddr);
Darren Harte4dc5b72009-03-12 00:56:13 -07001651 if (ret)
1652 goto out_put_key;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001653
Darren Harte4dc5b72009-03-12 00:56:13 -07001654 if (!fshared)
1655 goto retry_private;
1656
1657 put_futex_key(fshared, &q.key);
1658 goto retry;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001659}
1660
Darren Hartde87fcc2009-03-12 00:55:46 -07001661
Ingo Molnarc87e2832006-06-27 02:54:58 -07001662/*
Ingo Molnarc87e2832006-06-27 02:54:58 -07001663 * Userspace attempted a TID -> 0 atomic transition, and failed.
1664 * This is the in-kernel slowpath: we look up the PI state (if any),
1665 * and do the rt-mutex unlock.
1666 */
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001667static int futex_unlock_pi(u32 __user *uaddr, int fshared)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001668{
1669 struct futex_hash_bucket *hb;
1670 struct futex_q *this, *next;
1671 u32 uval;
Pierre Peifferec92d082007-05-09 02:35:00 -07001672 struct plist_head *head;
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001673 union futex_key key = FUTEX_KEY_INIT;
Darren Harte4dc5b72009-03-12 00:56:13 -07001674 int ret;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001675
1676retry:
1677 if (get_user(uval, uaddr))
1678 return -EFAULT;
1679 /*
1680 * We release only a lock we actually own:
1681 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001682 if ((uval & FUTEX_TID_MASK) != task_pid_vnr(current))
Ingo Molnarc87e2832006-06-27 02:54:58 -07001683 return -EPERM;
Ingo Molnarc87e2832006-06-27 02:54:58 -07001684
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001685 ret = get_futex_key(uaddr, fshared, &key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001686 if (unlikely(ret != 0))
1687 goto out;
1688
1689 hb = hash_futex(&key);
1690 spin_lock(&hb->lock);
1691
Ingo Molnarc87e2832006-06-27 02:54:58 -07001692 /*
1693 * To avoid races, try to do the TID -> 0 atomic transition
1694 * again. If it succeeds then we can return without waking
1695 * anyone else up:
1696 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001697 if (!(uval & FUTEX_OWNER_DIED))
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001698 uval = cmpxchg_futex_value_locked(uaddr, task_pid_vnr(current), 0);
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001699
Ingo Molnarc87e2832006-06-27 02:54:58 -07001700
1701 if (unlikely(uval == -EFAULT))
1702 goto pi_faulted;
1703 /*
1704 * Rare case: we managed to release the lock atomically,
1705 * no need to wake anyone else up:
1706 */
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001707 if (unlikely(uval == task_pid_vnr(current)))
Ingo Molnarc87e2832006-06-27 02:54:58 -07001708 goto out_unlock;
1709
1710 /*
1711 * Ok, other tasks may need to be woken up - check waiters
1712 * and do the wakeup if necessary:
1713 */
1714 head = &hb->chain;
1715
Pierre Peifferec92d082007-05-09 02:35:00 -07001716 plist_for_each_entry_safe(this, next, head, list) {
Ingo Molnarc87e2832006-06-27 02:54:58 -07001717 if (!match_futex (&this->key, &key))
1718 continue;
1719 ret = wake_futex_pi(uaddr, uval, this);
1720 /*
1721 * The atomic access to the futex value
1722 * generated a pagefault, so retry the
1723 * user-access and the wakeup:
1724 */
1725 if (ret == -EFAULT)
1726 goto pi_faulted;
1727 goto out_unlock;
1728 }
1729 /*
1730 * No waiters - kernel unlocks the futex:
1731 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001732 if (!(uval & FUTEX_OWNER_DIED)) {
1733 ret = unlock_futex_pi(uaddr, uval);
1734 if (ret == -EFAULT)
1735 goto pi_faulted;
1736 }
Ingo Molnarc87e2832006-06-27 02:54:58 -07001737
1738out_unlock:
1739 spin_unlock(&hb->lock);
Peter Zijlstra38d47c12008-09-26 19:32:20 +02001740 put_futex_key(fshared, &key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001741
Darren Hart42d35d42008-12-29 15:49:53 -08001742out:
Ingo Molnarc87e2832006-06-27 02:54:58 -07001743 return ret;
1744
1745pi_faulted:
1746 /*
Darren Hartb5686362008-12-18 15:06:34 -08001747 * We have to r/w *(int __user *)uaddr, and we have to modify it
1748 * atomically. Therefore, if we continue to fault after get_user()
1749 * below, we need to handle the fault ourselves, while still holding
1750 * the mmap_sem. This can occur if the uaddr is under contention as
1751 * we have to drop the mmap_sem in order to call get_user().
Ingo Molnarc87e2832006-06-27 02:54:58 -07001752 */
Alexey Kuznetsov778e9a92007-06-08 13:47:00 -07001753 spin_unlock(&hb->lock);
Darren Harte4dc5b72009-03-12 00:56:13 -07001754 put_futex_key(fshared, &key);
Ingo Molnarc87e2832006-06-27 02:54:58 -07001755
Ingo Molnarc87e2832006-06-27 02:54:58 -07001756 ret = get_user(uval, uaddr);
Darren Hartb5686362008-12-18 15:06:34 -08001757 if (!ret)
Ingo Molnarc87e2832006-06-27 02:54:58 -07001758 goto retry;
1759
Linus Torvalds1da177e2005-04-16 15:20:36 -07001760 return ret;
1761}
1762
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001763/*
1764 * Support for robust futexes: the kernel cleans up held futexes at
1765 * thread exit time.
1766 *
1767 * Implementation: user-space maintains a per-thread list of locks it
1768 * is holding. Upon do_exit(), the kernel carefully walks this list,
1769 * and marks all locks that are owned by this thread with the
Ingo Molnarc87e2832006-06-27 02:54:58 -07001770 * FUTEX_OWNER_DIED bit, and wakes up a waiter (if any). The list is
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001771 * always manipulated with the lock held, so the list is private and
1772 * per-thread. Userspace also maintains a per-thread 'list_op_pending'
1773 * field, to allow the kernel to clean up if the thread dies after
1774 * acquiring the lock, but just before it could have added itself to
1775 * the list. There can only be one such pending lock.
1776 */
1777
1778/**
1779 * sys_set_robust_list - set the robust-futex list head of a task
1780 * @head: pointer to the list-head
1781 * @len: length of the list-head, as userspace expects
1782 */
Heiko Carstens836f92a2009-01-14 14:14:33 +01001783SYSCALL_DEFINE2(set_robust_list, struct robust_list_head __user *, head,
1784 size_t, len)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001785{
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08001786 if (!futex_cmpxchg_enabled)
1787 return -ENOSYS;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001788 /*
1789 * The kernel knows only one size for now:
1790 */
1791 if (unlikely(len != sizeof(*head)))
1792 return -EINVAL;
1793
1794 current->robust_list = head;
1795
1796 return 0;
1797}
1798
1799/**
1800 * sys_get_robust_list - get the robust-futex list head of a task
1801 * @pid: pid of the process [zero for current task]
1802 * @head_ptr: pointer to a list-head pointer, the kernel fills it in
1803 * @len_ptr: pointer to a length field, the kernel fills in the header size
1804 */
Heiko Carstens836f92a2009-01-14 14:14:33 +01001805SYSCALL_DEFINE3(get_robust_list, int, pid,
1806 struct robust_list_head __user * __user *, head_ptr,
1807 size_t __user *, len_ptr)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001808{
Al Viroba46df92006-10-10 22:46:07 +01001809 struct robust_list_head __user *head;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001810 unsigned long ret;
David Howellsc69e8d92008-11-14 10:39:19 +11001811 const struct cred *cred = current_cred(), *pcred;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001812
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08001813 if (!futex_cmpxchg_enabled)
1814 return -ENOSYS;
1815
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001816 if (!pid)
1817 head = current->robust_list;
1818 else {
1819 struct task_struct *p;
1820
1821 ret = -ESRCH;
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07001822 rcu_read_lock();
Pavel Emelyanov228ebcb2007-10-18 23:40:16 -07001823 p = find_task_by_vpid(pid);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001824 if (!p)
1825 goto err_unlock;
1826 ret = -EPERM;
David Howellsc69e8d92008-11-14 10:39:19 +11001827 pcred = __task_cred(p);
1828 if (cred->euid != pcred->euid &&
1829 cred->euid != pcred->uid &&
David Howells76aac0e2008-11-14 10:39:12 +11001830 !capable(CAP_SYS_PTRACE))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001831 goto err_unlock;
1832 head = p->robust_list;
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07001833 rcu_read_unlock();
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001834 }
1835
1836 if (put_user(sizeof(*head), len_ptr))
1837 return -EFAULT;
1838 return put_user(head, head_ptr);
1839
1840err_unlock:
Oleg Nesterovaaa2a972006-09-29 02:00:55 -07001841 rcu_read_unlock();
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001842
1843 return ret;
1844}
1845
1846/*
1847 * Process a futex-list entry, check whether it's owned by the
1848 * dying task, and do notification if so:
1849 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001850int handle_futex_death(u32 __user *uaddr, struct task_struct *curr, int pi)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001851{
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001852 u32 uval, nval, mval;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001853
Ingo Molnar8f17d3a2006-03-27 01:16:27 -08001854retry:
1855 if (get_user(uval, uaddr))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001856 return -1;
1857
Pavel Emelyanovb4888932007-10-18 23:40:14 -07001858 if ((uval & FUTEX_TID_MASK) == task_pid_vnr(curr)) {
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001859 /*
1860 * Ok, this dying thread is truly holding a futex
1861 * of interest. Set the OWNER_DIED bit atomically
1862 * via cmpxchg, and if the value had FUTEX_WAITERS
1863 * set, wake up a waiter (if any). (We have to do a
1864 * futex_wake() even if OWNER_DIED is already set -
1865 * to handle the rare but possible case of recursive
1866 * thread-death.) The rest of the cleanup is done in
1867 * userspace.
1868 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001869 mval = (uval & FUTEX_WAITERS) | FUTEX_OWNER_DIED;
1870 nval = futex_atomic_cmpxchg_inatomic(uaddr, uval, mval);
1871
Ingo Molnarc87e2832006-06-27 02:54:58 -07001872 if (nval == -EFAULT)
1873 return -1;
1874
1875 if (nval != uval)
Ingo Molnar8f17d3a2006-03-27 01:16:27 -08001876 goto retry;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001877
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001878 /*
1879 * Wake robust non-PI futexes here. The wakeup of
1880 * PI futexes happens in exit_pi_state():
1881 */
Thomas Gleixner36cf3b52007-07-15 23:41:20 -07001882 if (!pi && (uval & FUTEX_WAITERS))
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001883 futex_wake(uaddr, 1, 1, FUTEX_BITSET_MATCH_ANY);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001884 }
1885 return 0;
1886}
1887
1888/*
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001889 * Fetch a robust-list pointer. Bit 0 signals PI futexes:
1890 */
1891static inline int fetch_robust_entry(struct robust_list __user **entry,
Al Viroba46df92006-10-10 22:46:07 +01001892 struct robust_list __user * __user *head,
1893 int *pi)
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001894{
1895 unsigned long uentry;
1896
Al Viroba46df92006-10-10 22:46:07 +01001897 if (get_user(uentry, (unsigned long __user *)head))
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001898 return -EFAULT;
1899
Al Viroba46df92006-10-10 22:46:07 +01001900 *entry = (void __user *)(uentry & ~1UL);
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001901 *pi = uentry & 1;
1902
1903 return 0;
1904}
1905
1906/*
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001907 * Walk curr->robust_list (very carefully, it's a userspace list!)
1908 * and mark any locks found there dead, and notify any waiters.
1909 *
1910 * We silently return on any sign of list-walking problem.
1911 */
1912void exit_robust_list(struct task_struct *curr)
1913{
1914 struct robust_list_head __user *head = curr->robust_list;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001915 struct robust_list __user *entry, *next_entry, *pending;
1916 unsigned int limit = ROBUST_LIST_LIMIT, pi, next_pi, pip;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001917 unsigned long futex_offset;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001918 int rc;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001919
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08001920 if (!futex_cmpxchg_enabled)
1921 return;
1922
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001923 /*
1924 * Fetch the list head (which was registered earlier, via
1925 * sys_set_robust_list()):
1926 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001927 if (fetch_robust_entry(&entry, &head->list.next, &pi))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001928 return;
1929 /*
1930 * Fetch the relative futex offset:
1931 */
1932 if (get_user(futex_offset, &head->futex_offset))
1933 return;
1934 /*
1935 * Fetch any possibly pending lock-add first, and handle it
1936 * if it exists:
1937 */
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001938 if (fetch_robust_entry(&pending, &head->list_op_pending, &pip))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001939 return;
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001940
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001941 next_entry = NULL; /* avoid warning with gcc */
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001942 while (entry != &head->list) {
1943 /*
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001944 * Fetch the next entry in the list before calling
1945 * handle_futex_death:
1946 */
1947 rc = fetch_robust_entry(&next_entry, &entry->next, &next_pi);
1948 /*
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001949 * A pending lock might already be on the list, so
Ingo Molnarc87e2832006-06-27 02:54:58 -07001950 * don't process it twice:
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001951 */
1952 if (entry != pending)
Al Viroba46df92006-10-10 22:46:07 +01001953 if (handle_futex_death((void __user *)entry + futex_offset,
Ingo Molnare3f2dde2006-07-29 05:17:57 +02001954 curr, pi))
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001955 return;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001956 if (rc)
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001957 return;
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001958 entry = next_entry;
1959 pi = next_pi;
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001960 /*
1961 * Avoid excessively long or circular lists:
1962 */
1963 if (!--limit)
1964 break;
1965
1966 cond_resched();
1967 }
Martin Schwidefsky9f96cb12007-10-01 01:20:13 -07001968
1969 if (pending)
1970 handle_futex_death((void __user *)pending + futex_offset,
1971 curr, pip);
Ingo Molnar0771dfe2006-03-27 01:16:22 -08001972}
1973
Pierre Peifferc19384b2007-05-09 02:35:02 -07001974long do_futex(u32 __user *uaddr, int op, u32 val, ktime_t *timeout,
Ingo Molnare2970f22006-06-27 02:54:47 -07001975 u32 __user *uaddr2, u32 val2, u32 val3)
Linus Torvalds1da177e2005-04-16 15:20:36 -07001976{
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001977 int clockrt, ret = -ENOSYS;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001978 int cmd = op & FUTEX_CMD_MASK;
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001979 int fshared = 0;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001980
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001981 if (!(op & FUTEX_PRIVATE_FLAG))
Peter Zijlstrac2f9f202008-09-26 19:32:23 +02001982 fshared = 1;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001983
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001984 clockrt = op & FUTEX_CLOCK_REALTIME;
1985 if (clockrt && cmd != FUTEX_WAIT_BITSET)
1986 return -ENOSYS;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07001987
1988 switch (cmd) {
Linus Torvalds1da177e2005-04-16 15:20:36 -07001989 case FUTEX_WAIT:
Thomas Gleixnercd689982008-02-01 17:45:14 +01001990 val3 = FUTEX_BITSET_MATCH_ANY;
1991 case FUTEX_WAIT_BITSET:
Thomas Gleixner1acdac12008-11-20 10:02:53 -08001992 ret = futex_wait(uaddr, fshared, val, timeout, val3, clockrt);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001993 break;
1994 case FUTEX_WAKE:
Thomas Gleixnercd689982008-02-01 17:45:14 +01001995 val3 = FUTEX_BITSET_MATCH_ANY;
1996 case FUTEX_WAKE_BITSET:
1997 ret = futex_wake(uaddr, fshared, val, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07001998 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07001999 case FUTEX_REQUEUE:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002000 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, NULL);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002001 break;
2002 case FUTEX_CMP_REQUEUE:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002003 ret = futex_requeue(uaddr, fshared, uaddr2, val, val2, &val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002004 break;
Jakub Jelinek4732efb2005-09-06 15:16:25 -07002005 case FUTEX_WAKE_OP:
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002006 ret = futex_wake_op(uaddr, fshared, uaddr2, val, val2, val3);
Jakub Jelinek4732efb2005-09-06 15:16:25 -07002007 break;
Ingo Molnarc87e2832006-06-27 02:54:58 -07002008 case FUTEX_LOCK_PI:
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002009 if (futex_cmpxchg_enabled)
2010 ret = futex_lock_pi(uaddr, fshared, val, timeout, 0);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002011 break;
2012 case FUTEX_UNLOCK_PI:
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002013 if (futex_cmpxchg_enabled)
2014 ret = futex_unlock_pi(uaddr, fshared);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002015 break;
2016 case FUTEX_TRYLOCK_PI:
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002017 if (futex_cmpxchg_enabled)
2018 ret = futex_lock_pi(uaddr, fshared, 0, timeout, 1);
Ingo Molnarc87e2832006-06-27 02:54:58 -07002019 break;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002020 default:
2021 ret = -ENOSYS;
2022 }
2023 return ret;
2024}
2025
2026
Heiko Carstens17da2bd2009-01-14 14:14:10 +01002027SYSCALL_DEFINE6(futex, u32 __user *, uaddr, int, op, u32, val,
2028 struct timespec __user *, utime, u32 __user *, uaddr2,
2029 u32, val3)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002030{
Pierre Peifferc19384b2007-05-09 02:35:02 -07002031 struct timespec ts;
2032 ktime_t t, *tp = NULL;
Ingo Molnare2970f22006-06-27 02:54:47 -07002033 u32 val2 = 0;
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002034 int cmd = op & FUTEX_CMD_MASK;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002035
Thomas Gleixnercd689982008-02-01 17:45:14 +01002036 if (utime && (cmd == FUTEX_WAIT || cmd == FUTEX_LOCK_PI ||
2037 cmd == FUTEX_WAIT_BITSET)) {
Pierre Peifferc19384b2007-05-09 02:35:02 -07002038 if (copy_from_user(&ts, utime, sizeof(ts)) != 0)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002039 return -EFAULT;
Pierre Peifferc19384b2007-05-09 02:35:02 -07002040 if (!timespec_valid(&ts))
Thomas Gleixner9741ef92006-03-31 02:31:32 -08002041 return -EINVAL;
Pierre Peifferc19384b2007-05-09 02:35:02 -07002042
2043 t = timespec_to_ktime(ts);
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002044 if (cmd == FUTEX_WAIT)
Thomas Gleixner5a7780e2008-02-13 09:20:43 +01002045 t = ktime_add_safe(ktime_get(), t);
Pierre Peifferc19384b2007-05-09 02:35:02 -07002046 tp = &t;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002047 }
2048 /*
Eric Dumazet34f01cc2007-05-09 02:35:04 -07002049 * requeue parameter in 'utime' if cmd == FUTEX_REQUEUE.
Andreas Schwabf54f0982007-07-31 00:38:51 -07002050 * number of waiters to wake in 'utime' if cmd == FUTEX_WAKE_OP.
Linus Torvalds1da177e2005-04-16 15:20:36 -07002051 */
Andreas Schwabf54f0982007-07-31 00:38:51 -07002052 if (cmd == FUTEX_REQUEUE || cmd == FUTEX_CMP_REQUEUE ||
2053 cmd == FUTEX_WAKE_OP)
Ingo Molnare2970f22006-06-27 02:54:47 -07002054 val2 = (u32) (unsigned long) utime;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002055
Pierre Peifferc19384b2007-05-09 02:35:02 -07002056 return do_futex(uaddr, op, val, tp, uaddr2, val2, val3);
Linus Torvalds1da177e2005-04-16 15:20:36 -07002057}
2058
Benjamin Herrenschmidtf6d107f2008-03-27 14:52:15 +11002059static int __init futex_init(void)
Linus Torvalds1da177e2005-04-16 15:20:36 -07002060{
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002061 u32 curval;
Thomas Gleixner3e4ab742008-02-23 15:23:55 -08002062 int i;
Linus Torvalds1da177e2005-04-16 15:20:36 -07002063
Thomas Gleixnera0c1e902008-02-23 15:23:57 -08002064 /*
2065 * This will fail and we want it. Some arch implementations do
2066 * runtime detection of the futex_atomic_cmpxchg_inatomic()
2067 * functionality. We want to know that before we call in any
2068 * of the complex code paths. Also we want to prevent
2069 * registration of robust lists in that case. NULL is
2070 * guaranteed to fault and we get -EFAULT on functional
2071 * implementation, the non functional ones will return
2072 * -ENOSYS.
2073 */
2074 curval = cmpxchg_futex_value_locked(NULL, 0, 0);
2075 if (curval == -EFAULT)
2076 futex_cmpxchg_enabled = 1;
2077
Thomas Gleixner3e4ab742008-02-23 15:23:55 -08002078 for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
2079 plist_head_init(&futex_queues[i].chain, &futex_queues[i].lock);
2080 spin_lock_init(&futex_queues[i].lock);
2081 }
2082
Linus Torvalds1da177e2005-04-16 15:20:36 -07002083 return 0;
2084}
Benjamin Herrenschmidtf6d107f2008-03-27 14:52:15 +11002085__initcall(futex_init);