Linux-2.6.12-rc2
Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
diff --git a/kernel/futex.c b/kernel/futex.c
new file mode 100644
index 0000000..7b54a67
--- /dev/null
+++ b/kernel/futex.c
@@ -0,0 +1,798 @@
+/*
+ * Fast Userspace Mutexes (which I call "Futexes!").
+ * (C) Rusty Russell, IBM 2002
+ *
+ * Generalized futexes, futex requeueing, misc fixes by Ingo Molnar
+ * (C) Copyright 2003 Red Hat Inc, All Rights Reserved
+ *
+ * Removed page pinning, fix privately mapped COW pages and other cleanups
+ * (C) Copyright 2003, 2004 Jamie Lokier
+ *
+ * Thanks to Ben LaHaise for yelling "hashed waitqueues" loudly
+ * enough at me, Linus for the original (flawed) idea, Matthew
+ * Kirkwood for proof-of-concept implementation.
+ *
+ * "The futexes are also cursed."
+ * "But they come in a choice of three flavours!"
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#include <linux/slab.h>
+#include <linux/poll.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/jhash.h>
+#include <linux/init.h>
+#include <linux/futex.h>
+#include <linux/mount.h>
+#include <linux/pagemap.h>
+#include <linux/syscalls.h>
+
+#define FUTEX_HASHBITS (CONFIG_BASE_SMALL ? 4 : 8)
+
+/*
+ * Futexes are matched on equal values of this key.
+ * The key type depends on whether it's a shared or private mapping.
+ * Don't rearrange members without looking at hash_futex().
+ *
+ * offset is aligned to a multiple of sizeof(u32) (== 4) by definition.
+ * We set bit 0 to indicate if it's an inode-based key.
+ */
+union futex_key {
+ struct {
+ unsigned long pgoff;
+ struct inode *inode;
+ int offset;
+ } shared;
+ struct {
+ unsigned long uaddr;
+ struct mm_struct *mm;
+ int offset;
+ } private;
+ struct {
+ unsigned long word;
+ void *ptr;
+ int offset;
+ } both;
+};
+
+/*
+ * We use this hashed waitqueue instead of a normal wait_queue_t, so
+ * we can wake only the relevant ones (hashed queues may be shared).
+ *
+ * A futex_q has a woken state, just like tasks have TASK_RUNNING.
+ * It is considered woken when list_empty(&q->list) || q->lock_ptr == 0.
+ * The order of wakup is always to make the first condition true, then
+ * wake up q->waiters, then make the second condition true.
+ */
+struct futex_q {
+ struct list_head list;
+ wait_queue_head_t waiters;
+
+ /* Which hash list lock to use. */
+ spinlock_t *lock_ptr;
+
+ /* Key which the futex is hashed on. */
+ union futex_key key;
+
+ /* For fd, sigio sent using these. */
+ int fd;
+ struct file *filp;
+};
+
+/*
+ * Split the global futex_lock into every hash list lock.
+ */
+struct futex_hash_bucket {
+ spinlock_t lock;
+ struct list_head chain;
+};
+
+static struct futex_hash_bucket futex_queues[1<<FUTEX_HASHBITS];
+
+/* Futex-fs vfsmount entry: */
+static struct vfsmount *futex_mnt;
+
+/*
+ * We hash on the keys returned from get_futex_key (see below).
+ */
+static struct futex_hash_bucket *hash_futex(union futex_key *key)
+{
+ u32 hash = jhash2((u32*)&key->both.word,
+ (sizeof(key->both.word)+sizeof(key->both.ptr))/4,
+ key->both.offset);
+ return &futex_queues[hash & ((1 << FUTEX_HASHBITS)-1)];
+}
+
+/*
+ * Return 1 if two futex_keys are equal, 0 otherwise.
+ */
+static inline int match_futex(union futex_key *key1, union futex_key *key2)
+{
+ return (key1->both.word == key2->both.word
+ && key1->both.ptr == key2->both.ptr
+ && key1->both.offset == key2->both.offset);
+}
+
+/*
+ * Get parameters which are the keys for a futex.
+ *
+ * For shared mappings, it's (page->index, vma->vm_file->f_dentry->d_inode,
+ * offset_within_page). For private mappings, it's (uaddr, current->mm).
+ * We can usually work out the index without swapping in the page.
+ *
+ * Returns: 0, or negative error code.
+ * The key words are stored in *key on success.
+ *
+ * Should be called with ¤t->mm->mmap_sem but NOT any spinlocks.
+ */
+static int get_futex_key(unsigned long uaddr, union futex_key *key)
+{
+ struct mm_struct *mm = current->mm;
+ struct vm_area_struct *vma;
+ struct page *page;
+ int err;
+
+ /*
+ * The futex address must be "naturally" aligned.
+ */
+ key->both.offset = uaddr % PAGE_SIZE;
+ if (unlikely((key->both.offset % sizeof(u32)) != 0))
+ return -EINVAL;
+ uaddr -= key->both.offset;
+
+ /*
+ * The futex is hashed differently depending on whether
+ * it's in a shared or private mapping. So check vma first.
+ */
+ vma = find_extend_vma(mm, uaddr);
+ if (unlikely(!vma))
+ return -EFAULT;
+
+ /*
+ * Permissions.
+ */
+ if (unlikely((vma->vm_flags & (VM_IO|VM_READ)) != VM_READ))
+ return (vma->vm_flags & VM_IO) ? -EPERM : -EACCES;
+
+ /*
+ * Private mappings are handled in a simple way.
+ *
+ * NOTE: When userspace waits on a MAP_SHARED mapping, even if
+ * it's a read-only handle, it's expected that futexes attach to
+ * the object not the particular process. Therefore we use
+ * VM_MAYSHARE here, not VM_SHARED which is restricted to shared
+ * mappings of _writable_ handles.
+ */
+ if (likely(!(vma->vm_flags & VM_MAYSHARE))) {
+ key->private.mm = mm;
+ key->private.uaddr = uaddr;
+ return 0;
+ }
+
+ /*
+ * Linear file mappings are also simple.
+ */
+ key->shared.inode = vma->vm_file->f_dentry->d_inode;
+ key->both.offset++; /* Bit 0 of offset indicates inode-based key. */
+ if (likely(!(vma->vm_flags & VM_NONLINEAR))) {
+ key->shared.pgoff = (((uaddr - vma->vm_start) >> PAGE_SHIFT)
+ + vma->vm_pgoff);
+ return 0;
+ }
+
+ /*
+ * We could walk the page table to read the non-linear
+ * pte, and get the page index without fetching the page
+ * from swap. But that's a lot of code to duplicate here
+ * for a rare case, so we simply fetch the page.
+ */
+
+ /*
+ * Do a quick atomic lookup first - this is the fastpath.
+ */
+ spin_lock(¤t->mm->page_table_lock);
+ page = follow_page(mm, uaddr, 0);
+ if (likely(page != NULL)) {
+ key->shared.pgoff =
+ page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ spin_unlock(¤t->mm->page_table_lock);
+ return 0;
+ }
+ spin_unlock(¤t->mm->page_table_lock);
+
+ /*
+ * Do it the general way.
+ */
+ err = get_user_pages(current, mm, uaddr, 1, 0, 0, &page, NULL);
+ if (err >= 0) {
+ key->shared.pgoff =
+ page->index << (PAGE_CACHE_SHIFT - PAGE_SHIFT);
+ put_page(page);
+ return 0;
+ }
+ return err;
+}
+
+/*
+ * Take a reference to the resource addressed by a key.
+ * Can be called while holding spinlocks.
+ *
+ * NOTE: mmap_sem MUST be held between get_futex_key() and calling this
+ * function, if it is called at all. mmap_sem keeps key->shared.inode valid.
+ */
+static inline void get_key_refs(union futex_key *key)
+{
+ if (key->both.ptr != 0) {
+ if (key->both.offset & 1)
+ atomic_inc(&key->shared.inode->i_count);
+ else
+ atomic_inc(&key->private.mm->mm_count);
+ }
+}
+
+/*
+ * Drop a reference to the resource addressed by a key.
+ * The hash bucket spinlock must not be held.
+ */
+static void drop_key_refs(union futex_key *key)
+{
+ if (key->both.ptr != 0) {
+ if (key->both.offset & 1)
+ iput(key->shared.inode);
+ else
+ mmdrop(key->private.mm);
+ }
+}
+
+static inline int get_futex_value_locked(int *dest, int __user *from)
+{
+ int ret;
+
+ inc_preempt_count();
+ ret = __copy_from_user_inatomic(dest, from, sizeof(int));
+ dec_preempt_count();
+
+ return ret ? -EFAULT : 0;
+}
+
+/*
+ * The hash bucket lock must be held when this is called.
+ * Afterwards, the futex_q must not be accessed.
+ */
+static void wake_futex(struct futex_q *q)
+{
+ list_del_init(&q->list);
+ if (q->filp)
+ send_sigio(&q->filp->f_owner, q->fd, POLL_IN);
+ /*
+ * The lock in wake_up_all() is a crucial memory barrier after the
+ * list_del_init() and also before assigning to q->lock_ptr.
+ */
+ wake_up_all(&q->waiters);
+ /*
+ * The waiting task can free the futex_q as soon as this is written,
+ * without taking any locks. This must come last.
+ */
+ q->lock_ptr = NULL;
+}
+
+/*
+ * Wake up all waiters hashed on the physical page that is mapped
+ * to this virtual address:
+ */
+static int futex_wake(unsigned long uaddr, int nr_wake)
+{
+ union futex_key key;
+ struct futex_hash_bucket *bh;
+ struct list_head *head;
+ struct futex_q *this, *next;
+ int ret;
+
+ down_read(¤t->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr, &key);
+ if (unlikely(ret != 0))
+ goto out;
+
+ bh = hash_futex(&key);
+ spin_lock(&bh->lock);
+ head = &bh->chain;
+
+ list_for_each_entry_safe(this, next, head, list) {
+ if (match_futex (&this->key, &key)) {
+ wake_futex(this);
+ if (++ret >= nr_wake)
+ break;
+ }
+ }
+
+ spin_unlock(&bh->lock);
+out:
+ up_read(¤t->mm->mmap_sem);
+ return ret;
+}
+
+/*
+ * Requeue all waiters hashed on one physical page to another
+ * physical page.
+ */
+static int futex_requeue(unsigned long uaddr1, unsigned long uaddr2,
+ int nr_wake, int nr_requeue, int *valp)
+{
+ union futex_key key1, key2;
+ struct futex_hash_bucket *bh1, *bh2;
+ struct list_head *head1;
+ struct futex_q *this, *next;
+ int ret, drop_count = 0;
+
+ retry:
+ down_read(¤t->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr1, &key1);
+ if (unlikely(ret != 0))
+ goto out;
+ ret = get_futex_key(uaddr2, &key2);
+ if (unlikely(ret != 0))
+ goto out;
+
+ bh1 = hash_futex(&key1);
+ bh2 = hash_futex(&key2);
+
+ if (bh1 < bh2)
+ spin_lock(&bh1->lock);
+ spin_lock(&bh2->lock);
+ if (bh1 > bh2)
+ spin_lock(&bh1->lock);
+
+ if (likely(valp != NULL)) {
+ int curval;
+
+ ret = get_futex_value_locked(&curval, (int __user *)uaddr1);
+
+ if (unlikely(ret)) {
+ spin_unlock(&bh1->lock);
+ if (bh1 != bh2)
+ spin_unlock(&bh2->lock);
+
+ /* If we would have faulted, release mmap_sem, fault
+ * it in and start all over again.
+ */
+ up_read(¤t->mm->mmap_sem);
+
+ ret = get_user(curval, (int __user *)uaddr1);
+
+ if (!ret)
+ goto retry;
+
+ return ret;
+ }
+ if (curval != *valp) {
+ ret = -EAGAIN;
+ goto out_unlock;
+ }
+ }
+
+ head1 = &bh1->chain;
+ list_for_each_entry_safe(this, next, head1, list) {
+ if (!match_futex (&this->key, &key1))
+ continue;
+ if (++ret <= nr_wake) {
+ wake_futex(this);
+ } else {
+ list_move_tail(&this->list, &bh2->chain);
+ this->lock_ptr = &bh2->lock;
+ this->key = key2;
+ get_key_refs(&key2);
+ drop_count++;
+
+ if (ret - nr_wake >= nr_requeue)
+ break;
+ /* Make sure to stop if key1 == key2 */
+ if (head1 == &bh2->chain && head1 != &next->list)
+ head1 = &this->list;
+ }
+ }
+
+out_unlock:
+ spin_unlock(&bh1->lock);
+ if (bh1 != bh2)
+ spin_unlock(&bh2->lock);
+
+ /* drop_key_refs() must be called outside the spinlocks. */
+ while (--drop_count >= 0)
+ drop_key_refs(&key1);
+
+out:
+ up_read(¤t->mm->mmap_sem);
+ return ret;
+}
+
+/* The key must be already stored in q->key. */
+static inline struct futex_hash_bucket *
+queue_lock(struct futex_q *q, int fd, struct file *filp)
+{
+ struct futex_hash_bucket *bh;
+
+ q->fd = fd;
+ q->filp = filp;
+
+ init_waitqueue_head(&q->waiters);
+
+ get_key_refs(&q->key);
+ bh = hash_futex(&q->key);
+ q->lock_ptr = &bh->lock;
+
+ spin_lock(&bh->lock);
+ return bh;
+}
+
+static inline void __queue_me(struct futex_q *q, struct futex_hash_bucket *bh)
+{
+ list_add_tail(&q->list, &bh->chain);
+ spin_unlock(&bh->lock);
+}
+
+static inline void
+queue_unlock(struct futex_q *q, struct futex_hash_bucket *bh)
+{
+ spin_unlock(&bh->lock);
+ drop_key_refs(&q->key);
+}
+
+/*
+ * queue_me and unqueue_me must be called as a pair, each
+ * exactly once. They are called with the hashed spinlock held.
+ */
+
+/* The key must be already stored in q->key. */
+static void queue_me(struct futex_q *q, int fd, struct file *filp)
+{
+ struct futex_hash_bucket *bh;
+ bh = queue_lock(q, fd, filp);
+ __queue_me(q, bh);
+}
+
+/* Return 1 if we were still queued (ie. 0 means we were woken) */
+static int unqueue_me(struct futex_q *q)
+{
+ int ret = 0;
+ spinlock_t *lock_ptr;
+
+ /* In the common case we don't take the spinlock, which is nice. */
+ retry:
+ lock_ptr = q->lock_ptr;
+ if (lock_ptr != 0) {
+ spin_lock(lock_ptr);
+ /*
+ * q->lock_ptr can change between reading it and
+ * spin_lock(), causing us to take the wrong lock. This
+ * corrects the race condition.
+ *
+ * Reasoning goes like this: if we have the wrong lock,
+ * q->lock_ptr must have changed (maybe several times)
+ * between reading it and the spin_lock(). It can
+ * change again after the spin_lock() but only if it was
+ * already changed before the spin_lock(). It cannot,
+ * however, change back to the original value. Therefore
+ * we can detect whether we acquired the correct lock.
+ */
+ if (unlikely(lock_ptr != q->lock_ptr)) {
+ spin_unlock(lock_ptr);
+ goto retry;
+ }
+ WARN_ON(list_empty(&q->list));
+ list_del(&q->list);
+ spin_unlock(lock_ptr);
+ ret = 1;
+ }
+
+ drop_key_refs(&q->key);
+ return ret;
+}
+
+static int futex_wait(unsigned long uaddr, int val, unsigned long time)
+{
+ DECLARE_WAITQUEUE(wait, current);
+ int ret, curval;
+ struct futex_q q;
+ struct futex_hash_bucket *bh;
+
+ retry:
+ down_read(¤t->mm->mmap_sem);
+
+ ret = get_futex_key(uaddr, &q.key);
+ if (unlikely(ret != 0))
+ goto out_release_sem;
+
+ bh = queue_lock(&q, -1, NULL);
+
+ /*
+ * Access the page AFTER the futex is queued.
+ * Order is important:
+ *
+ * Userspace waiter: val = var; if (cond(val)) futex_wait(&var, val);
+ * Userspace waker: if (cond(var)) { var = new; futex_wake(&var); }
+ *
+ * The basic logical guarantee of a futex is that it blocks ONLY
+ * if cond(var) is known to be true at the time of blocking, for
+ * any cond. If we queued after testing *uaddr, that would open
+ * a race condition where we could block indefinitely with
+ * cond(var) false, which would violate the guarantee.
+ *
+ * A consequence is that futex_wait() can return zero and absorb
+ * a wakeup when *uaddr != val on entry to the syscall. This is
+ * rare, but normal.
+ *
+ * We hold the mmap semaphore, so the mapping cannot have changed
+ * since we looked it up in get_futex_key.
+ */
+
+ ret = get_futex_value_locked(&curval, (int __user *)uaddr);
+
+ if (unlikely(ret)) {
+ queue_unlock(&q, bh);
+
+ /* If we would have faulted, release mmap_sem, fault it in and
+ * start all over again.
+ */
+ up_read(¤t->mm->mmap_sem);
+
+ ret = get_user(curval, (int __user *)uaddr);
+
+ if (!ret)
+ goto retry;
+ return ret;
+ }
+ if (curval != val) {
+ ret = -EWOULDBLOCK;
+ queue_unlock(&q, bh);
+ goto out_release_sem;
+ }
+
+ /* Only actually queue if *uaddr contained val. */
+ __queue_me(&q, bh);
+
+ /*
+ * Now the futex is queued and we have checked the data, we
+ * don't want to hold mmap_sem while we sleep.
+ */
+ up_read(¤t->mm->mmap_sem);
+
+ /*
+ * There might have been scheduling since the queue_me(), as we
+ * cannot hold a spinlock across the get_user() in case it
+ * faults, and we cannot just set TASK_INTERRUPTIBLE state when
+ * queueing ourselves into the futex hash. This code thus has to
+ * rely on the futex_wake() code removing us from hash when it
+ * wakes us up.
+ */
+
+ /* add_wait_queue is the barrier after __set_current_state. */
+ __set_current_state(TASK_INTERRUPTIBLE);
+ add_wait_queue(&q.waiters, &wait);
+ /*
+ * !list_empty() is safe here without any lock.
+ * q.lock_ptr != 0 is not safe, because of ordering against wakeup.
+ */
+ if (likely(!list_empty(&q.list)))
+ time = schedule_timeout(time);
+ __set_current_state(TASK_RUNNING);
+
+ /*
+ * NOTE: we don't remove ourselves from the waitqueue because
+ * we are the only user of it.
+ */
+
+ /* If we were woken (and unqueued), we succeeded, whatever. */
+ if (!unqueue_me(&q))
+ return 0;
+ if (time == 0)
+ return -ETIMEDOUT;
+ /* We expect signal_pending(current), but another thread may
+ * have handled it for us already. */
+ return -EINTR;
+
+ out_release_sem:
+ up_read(¤t->mm->mmap_sem);
+ return ret;
+}
+
+static int futex_close(struct inode *inode, struct file *filp)
+{
+ struct futex_q *q = filp->private_data;
+
+ unqueue_me(q);
+ kfree(q);
+ return 0;
+}
+
+/* This is one-shot: once it's gone off you need a new fd */
+static unsigned int futex_poll(struct file *filp,
+ struct poll_table_struct *wait)
+{
+ struct futex_q *q = filp->private_data;
+ int ret = 0;
+
+ poll_wait(filp, &q->waiters, wait);
+
+ /*
+ * list_empty() is safe here without any lock.
+ * q->lock_ptr != 0 is not safe, because of ordering against wakeup.
+ */
+ if (list_empty(&q->list))
+ ret = POLLIN | POLLRDNORM;
+
+ return ret;
+}
+
+static struct file_operations futex_fops = {
+ .release = futex_close,
+ .poll = futex_poll,
+};
+
+/*
+ * Signal allows caller to avoid the race which would occur if they
+ * set the sigio stuff up afterwards.
+ */
+static int futex_fd(unsigned long uaddr, int signal)
+{
+ struct futex_q *q;
+ struct file *filp;
+ int ret, err;
+
+ ret = -EINVAL;
+ if (signal < 0 || signal > _NSIG)
+ goto out;
+
+ ret = get_unused_fd();
+ if (ret < 0)
+ goto out;
+ filp = get_empty_filp();
+ if (!filp) {
+ put_unused_fd(ret);
+ ret = -ENFILE;
+ goto out;
+ }
+ filp->f_op = &futex_fops;
+ filp->f_vfsmnt = mntget(futex_mnt);
+ filp->f_dentry = dget(futex_mnt->mnt_root);
+ filp->f_mapping = filp->f_dentry->d_inode->i_mapping;
+
+ if (signal) {
+ int err;
+ err = f_setown(filp, current->pid, 1);
+ if (err < 0) {
+ put_unused_fd(ret);
+ put_filp(filp);
+ ret = err;
+ goto out;
+ }
+ filp->f_owner.signum = signal;
+ }
+
+ q = kmalloc(sizeof(*q), GFP_KERNEL);
+ if (!q) {
+ put_unused_fd(ret);
+ put_filp(filp);
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ down_read(¤t->mm->mmap_sem);
+ err = get_futex_key(uaddr, &q->key);
+
+ if (unlikely(err != 0)) {
+ up_read(¤t->mm->mmap_sem);
+ put_unused_fd(ret);
+ put_filp(filp);
+ kfree(q);
+ return err;
+ }
+
+ /*
+ * queue_me() must be called before releasing mmap_sem, because
+ * key->shared.inode needs to be referenced while holding it.
+ */
+ filp->private_data = q;
+
+ queue_me(q, ret, filp);
+ up_read(¤t->mm->mmap_sem);
+
+ /* Now we map fd to filp, so userspace can access it */
+ fd_install(ret, filp);
+out:
+ return ret;
+}
+
+long do_futex(unsigned long uaddr, int op, int val, unsigned long timeout,
+ unsigned long uaddr2, int val2, int val3)
+{
+ int ret;
+
+ switch (op) {
+ case FUTEX_WAIT:
+ ret = futex_wait(uaddr, val, timeout);
+ break;
+ case FUTEX_WAKE:
+ ret = futex_wake(uaddr, val);
+ break;
+ case FUTEX_FD:
+ /* non-zero val means F_SETOWN(getpid()) & F_SETSIG(val) */
+ ret = futex_fd(uaddr, val);
+ break;
+ case FUTEX_REQUEUE:
+ ret = futex_requeue(uaddr, uaddr2, val, val2, NULL);
+ break;
+ case FUTEX_CMP_REQUEUE:
+ ret = futex_requeue(uaddr, uaddr2, val, val2, &val3);
+ break;
+ default:
+ ret = -ENOSYS;
+ }
+ return ret;
+}
+
+
+asmlinkage long sys_futex(u32 __user *uaddr, int op, int val,
+ struct timespec __user *utime, u32 __user *uaddr2,
+ int val3)
+{
+ struct timespec t;
+ unsigned long timeout = MAX_SCHEDULE_TIMEOUT;
+ int val2 = 0;
+
+ if ((op == FUTEX_WAIT) && utime) {
+ if (copy_from_user(&t, utime, sizeof(t)) != 0)
+ return -EFAULT;
+ timeout = timespec_to_jiffies(&t) + 1;
+ }
+ /*
+ * requeue parameter in 'utime' if op == FUTEX_REQUEUE.
+ */
+ if (op >= FUTEX_REQUEUE)
+ val2 = (int) (unsigned long) utime;
+
+ return do_futex((unsigned long)uaddr, op, val, timeout,
+ (unsigned long)uaddr2, val2, val3);
+}
+
+static struct super_block *
+futexfs_get_sb(struct file_system_type *fs_type,
+ int flags, const char *dev_name, void *data)
+{
+ return get_sb_pseudo(fs_type, "futex", NULL, 0xBAD1DEA);
+}
+
+static struct file_system_type futex_fs_type = {
+ .name = "futexfs",
+ .get_sb = futexfs_get_sb,
+ .kill_sb = kill_anon_super,
+};
+
+static int __init init(void)
+{
+ unsigned int i;
+
+ register_filesystem(&futex_fs_type);
+ futex_mnt = kern_mount(&futex_fs_type);
+
+ for (i = 0; i < ARRAY_SIZE(futex_queues); i++) {
+ INIT_LIST_HEAD(&futex_queues[i].chain);
+ spin_lock_init(&futex_queues[i].lock);
+ }
+ return 0;
+}
+__initcall(init);
