kernel/events/ring_buffer.c - maze/linux - Git at Google

 /*
  * Performance events ring-buffer code:
  *
  *  Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
  *  Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
  *  Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
  *  Copyright  ©  2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
  *
  * For licensing details see kernel-base/COPYING
  */

 #include <linux/perf_event.h>
 #include <linux/vmalloc.h>
 #include <linux/slab.h>

 #include "internal.h"

 static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
 			      unsigned long offset, unsigned long head)
 {
 	unsigned long sz = perf_data_size(rb);
 	unsigned long mask = sz - 1;

 	/*
 	 * check if user-writable
 	 * overwrite : over-write its own tail
 	 * !overwrite: buffer possibly drops events.
 	 */
 	if (rb->overwrite)
 		return true;

 	/*
 	 * verify that payload is not bigger than buffer
 	 * otherwise masking logic may fail to detect
 	 * the "not enough space" condition
 	 */
 	if ((head - offset) > sz)
 		return false;

 	offset = (offset - tail) & mask;
 	head   = (head   - tail) & mask;

 	if ((int)(head - offset) < 0)
 		return false;

 	return true;
 }

 static void perf_output_wakeup(struct perf_output_handle *handle)
 {
 	atomic_set(&handle->rb->poll, POLL_IN);

 	handle->event->pending_wakeup = 1;
 	irq_work_queue(&handle->event->pending);
 }

 /*
  * We need to ensure a later event_id doesn't publish a head when a former
  * event isn't done writing. However since we need to deal with NMIs we
  * cannot fully serialize things.
  *
  * We only publish the head (and generate a wakeup) when the outer-most
  * event completes.
  */
 static void perf_output_get_handle(struct perf_output_handle *handle)
 {
 	struct ring_buffer *rb = handle->rb;

 	preempt_disable();
 	local_inc(&rb->nest);
 	handle->wakeup = local_read(&rb->wakeup);
 }

 static void perf_output_put_handle(struct perf_output_handle *handle)
 {
 	struct ring_buffer *rb = handle->rb;
 	unsigned long head;

 again:
 	head = local_read(&rb->head);

 	/*
 	 * IRQ/NMI can happen here, which means we can miss a head update.
 	 */

 	if (!local_dec_and_test(&rb->nest))
 		goto out;

 	/*
 	 * Publish the known good head. Rely on the full barrier implied
 	 * by atomic_dec_and_test() order the rb->head read and this
 	 * write.
 	 */
 	rb->user_page->data_head = head;

 	/*
 	 * Now check if we missed an update, rely on the (compiler)
 	 * barrier in atomic_dec_and_test() to re-read rb->head.
 	 */
 	if (unlikely(head != local_read(&rb->head))) {
 		local_inc(&rb->nest);
 		goto again;
 	}

 	if (handle->wakeup != local_read(&rb->wakeup))
 		perf_output_wakeup(handle);

 out:
 	preempt_enable();
 }

 int perf_output_begin(struct perf_output_handle *handle,
 		      struct perf_event *event, unsigned int size)
 {
 	struct ring_buffer *rb;
 	unsigned long tail, offset, head;
 	int have_lost;
 	struct perf_sample_data sample_data;
 	struct {
 		struct perf_event_header header;
 		u64			 id;
 		u64			 lost;
 	} lost_event;

 	rcu_read_lock();
 	/*
 	 * For inherited events we send all the output towards the parent.
 	 */
 	if (event->parent)
 		event = event->parent;

 	rb = rcu_dereference(event->rb);
 	if (!rb)
 		goto out;

 	handle->rb	= rb;
 	handle->event	= event;

 	if (!rb->nr_pages)
 		goto out;

 	have_lost = local_read(&rb->lost);
 	if (have_lost) {
 		lost_event.header.size = sizeof(lost_event);
 		perf_event_header__init_id(&lost_event.header, &sample_data,
 					   event);
 		size += lost_event.header.size;
 	}

 	perf_output_get_handle(handle);

 	do {
 		/*
 		 * Userspace could choose to issue a mb() before updating the
 		 * tail pointer. So that all reads will be completed before the
 		 * write is issued.
 		 */
 		tail = ACCESS_ONCE(rb->user_page->data_tail);
 		smp_rmb();
 		offset = head = local_read(&rb->head);
 		head += size;
 		if (unlikely(!perf_output_space(rb, tail, offset, head)))
 			goto fail;
 	} while (local_cmpxchg(&rb->head, offset, head) != offset);

 	if (head - local_read(&rb->wakeup) > rb->watermark)
 		local_add(rb->watermark, &rb->wakeup);

 	handle->page = offset >> (PAGE_SHIFT + page_order(rb));
 	handle->page &= rb->nr_pages - 1;
 	handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
 	handle->addr = rb->data_pages[handle->page];
 	handle->addr += handle->size;
 	handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;

 	if (have_lost) {
 		lost_event.header.type = PERF_RECORD_LOST;
 		lost_event.header.misc = 0;
 		lost_event.id          = event->id;
 		lost_event.lost        = local_xchg(&rb->lost, 0);

 		perf_output_put(handle, lost_event);
 		perf_event__output_id_sample(event, handle, &sample_data);
 	}

 	return 0;

 fail:
 	local_inc(&rb->lost);
 	perf_output_put_handle(handle);
 out:
 	rcu_read_unlock();

 	return -ENOSPC;
 }

 unsigned int perf_output_copy(struct perf_output_handle *handle,
 		      const void *buf, unsigned int len)
 {
 	return __output_copy(handle, buf, len);
 }

 unsigned int perf_output_skip(struct perf_output_handle *handle,
 			      unsigned int len)
 {
 	return __output_skip(handle, NULL, len);
 }

 void perf_output_end(struct perf_output_handle *handle)
 {
 	perf_output_put_handle(handle);
 	rcu_read_unlock();
 }

 static void
 ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
 {
 	long max_size = perf_data_size(rb);

 	if (watermark)
 		rb->watermark = min(max_size, watermark);

 	if (!rb->watermark)
 		rb->watermark = max_size / 2;

 	if (flags & RING_BUFFER_WRITABLE)
 		rb->overwrite = 0;
 	else
 		rb->overwrite = 1;

 	atomic_set(&rb->refcount, 1);

 	INIT_LIST_HEAD(&rb->event_list);
 	spin_lock_init(&rb->event_lock);
 }

 #ifndef CONFIG_PERF_USE_VMALLOC

 /*
  * Back perf_mmap() with regular GFP_KERNEL-0 pages.
  */

 struct page *
 perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
 {
 	if (pgoff > rb->nr_pages)
 		return NULL;

 	if (pgoff == 0)
 		return virt_to_page(rb->user_page);

 	return virt_to_page(rb->data_pages[pgoff - 1]);
 }

 static void *perf_mmap_alloc_page(int cpu)
 {
 	struct page *page;
 	int node;

 	node = (cpu == -1) ? cpu : cpu_to_node(cpu);
 	page = alloc_pages_node(node, GFP_KERNEL | __GFP_ZERO, 0);
 	if (!page)
 		return NULL;

 	return page_address(page);
 }

 struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
 {
 	struct ring_buffer *rb;
 	unsigned long size;
 	int i;

 	size = sizeof(struct ring_buffer);
 	size += nr_pages * sizeof(void *);

 	rb = kzalloc(size, GFP_KERNEL);
 	if (!rb)
 		goto fail;

 	rb->user_page = perf_mmap_alloc_page(cpu);
 	if (!rb->user_page)
 		goto fail_user_page;

 	for (i = 0; i < nr_pages; i++) {
 		rb->data_pages[i] = perf_mmap_alloc_page(cpu);
 		if (!rb->data_pages[i])
 			goto fail_data_pages;
 	}

 	rb->nr_pages = nr_pages;

 	ring_buffer_init(rb, watermark, flags);

 	return rb;

 fail_data_pages:
 	for (i--; i >= 0; i--)
 		free_page((unsigned long)rb->data_pages[i]);

 	free_page((unsigned long)rb->user_page);

 fail_user_page:
 	kfree(rb);

 fail:
 	return NULL;
 }

 static void perf_mmap_free_page(unsigned long addr)
 {
 	struct page *page = virt_to_page((void *)addr);

 	page->mapping = NULL;
 	__free_page(page);
 }

 void rb_free(struct ring_buffer *rb)
 {
 	int i;

 	perf_mmap_free_page((unsigned long)rb->user_page);
 	for (i = 0; i < rb->nr_pages; i++)
 		perf_mmap_free_page((unsigned long)rb->data_pages[i]);
 	kfree(rb);
 }

 #else
 static int data_page_nr(struct ring_buffer *rb)
 {
 	return rb->nr_pages << page_order(rb);
 }

 struct page *
 perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
 {
 	/* The '>' counts in the user page. */
 	if (pgoff > data_page_nr(rb))
 		return NULL;

 	return vmalloc_to_page((void *)rb->user_page + pgoff * PAGE_SIZE);
 }

 static void perf_mmap_unmark_page(void *addr)
 {
 	struct page *page = vmalloc_to_page(addr);

 	page->mapping = NULL;
 }

 static void rb_free_work(struct work_struct *work)
 {
 	struct ring_buffer *rb;
 	void *base;
 	int i, nr;

 	rb = container_of(work, struct ring_buffer, work);
 	nr = data_page_nr(rb);

 	base = rb->user_page;
 	/* The '<=' counts in the user page. */
 	for (i = 0; i <= nr; i++)
 		perf_mmap_unmark_page(base + (i * PAGE_SIZE));

 	vfree(base);
 	kfree(rb);
 }

 void rb_free(struct ring_buffer *rb)
 {
 	schedule_work(&rb->work);
 }

 struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
 {
 	struct ring_buffer *rb;
 	unsigned long size;
 	void *all_buf;

 	size = sizeof(struct ring_buffer);
 	size += sizeof(void *);

 	rb = kzalloc(size, GFP_KERNEL);
 	if (!rb)
 		goto fail;

 	INIT_WORK(&rb->work, rb_free_work);

 	all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
 	if (!all_buf)
 		goto fail_all_buf;

 	rb->user_page = all_buf;
 	rb->data_pages[0] = all_buf + PAGE_SIZE;
 	rb->page_order = ilog2(nr_pages);
 	rb->nr_pages = !!nr_pages;

 	ring_buffer_init(rb, watermark, flags);

 	return rb;

 fail_all_buf:
 	kfree(rb);

 fail:
 	return NULL;
 }

 #endif
	/*
	* Performance events ring-buffer code:
	*
	* Copyright (C) 2008 Thomas Gleixner <tglx@linutronix.de>
	* Copyright (C) 2008-2011 Red Hat, Inc., Ingo Molnar
	* Copyright (C) 2008-2011 Red Hat, Inc., Peter Zijlstra <pzijlstr@redhat.com>
	* Copyright © 2009 Paul Mackerras, IBM Corp. <paulus@au1.ibm.com>
	*
	* For licensing details see kernel-base/COPYING
	*/

	#include <linux/perf_event.h>
	#include <linux/vmalloc.h>
	#include <linux/slab.h>

	#include "internal.h"

	static bool perf_output_space(struct ring_buffer *rb, unsigned long tail,
	unsigned long offset, unsigned long head)
	{
	unsigned long sz = perf_data_size(rb);
	unsigned long mask = sz - 1;

	/*
	* check if user-writable
	* overwrite : over-write its own tail
	* !overwrite: buffer possibly drops events.
	*/
	if (rb->overwrite)
	return true;

	/*
	* verify that payload is not bigger than buffer
	* otherwise masking logic may fail to detect
	* the "not enough space" condition
	*/
	if ((head - offset) > sz)
	return false;

	offset = (offset - tail) & mask;
	head = (head - tail) & mask;

	if ((int)(head - offset) < 0)
	return false;

	return true;
	}

	static void perf_output_wakeup(struct perf_output_handle *handle)
	{
	atomic_set(&handle->rb->poll, POLL_IN);

	handle->event->pending_wakeup = 1;
	irq_work_queue(&handle->event->pending);
	}

	/*
	* We need to ensure a later event_id doesn't publish a head when a former
	* event isn't done writing. However since we need to deal with NMIs we
	* cannot fully serialize things.
	*
	* We only publish the head (and generate a wakeup) when the outer-most
	* event completes.
	*/
	static void perf_output_get_handle(struct perf_output_handle *handle)
	{
	struct ring_buffer *rb = handle->rb;

	preempt_disable();
	local_inc(&rb->nest);
	handle->wakeup = local_read(&rb->wakeup);
	}

	static void perf_output_put_handle(struct perf_output_handle *handle)
	{
	struct ring_buffer *rb = handle->rb;
	unsigned long head;

	again:
	head = local_read(&rb->head);

	/*
	* IRQ/NMI can happen here, which means we can miss a head update.
	*/

	if (!local_dec_and_test(&rb->nest))
	goto out;

	/*
	* Publish the known good head. Rely on the full barrier implied
	* by atomic_dec_and_test() order the rb->head read and this
	* write.
	*/
	rb->user_page->data_head = head;

	/*
	* Now check if we missed an update, rely on the (compiler)
	* barrier in atomic_dec_and_test() to re-read rb->head.
	*/
	if (unlikely(head != local_read(&rb->head))) {
	local_inc(&rb->nest);
	goto again;
	}

	if (handle->wakeup != local_read(&rb->wakeup))
	perf_output_wakeup(handle);

	out:
	preempt_enable();
	}

	int perf_output_begin(struct perf_output_handle *handle,
	struct perf_event *event, unsigned int size)
	{
	struct ring_buffer *rb;
	unsigned long tail, offset, head;
	int have_lost;
	struct perf_sample_data sample_data;
	struct {
	struct perf_event_header header;
	u64 id;
	u64 lost;
	} lost_event;

	rcu_read_lock();
	/*
	* For inherited events we send all the output towards the parent.
	*/
	if (event->parent)
	event = event->parent;

	rb = rcu_dereference(event->rb);
	if (!rb)
	goto out;

	handle->rb = rb;
	handle->event = event;

	if (!rb->nr_pages)
	goto out;

	have_lost = local_read(&rb->lost);
	if (have_lost) {
	lost_event.header.size = sizeof(lost_event);
	perf_event_header__init_id(&lost_event.header, &sample_data,
	event);
	size += lost_event.header.size;
	}

	perf_output_get_handle(handle);

	do {
	/*
	* Userspace could choose to issue a mb() before updating the
	* tail pointer. So that all reads will be completed before the
	* write is issued.
	*/
	tail = ACCESS_ONCE(rb->user_page->data_tail);
	smp_rmb();
	offset = head = local_read(&rb->head);
	head += size;
	if (unlikely(!perf_output_space(rb, tail, offset, head)))
	goto fail;
	} while (local_cmpxchg(&rb->head, offset, head) != offset);

	if (head - local_read(&rb->wakeup) > rb->watermark)
	local_add(rb->watermark, &rb->wakeup);

	handle->page = offset >> (PAGE_SHIFT + page_order(rb));
	handle->page &= rb->nr_pages - 1;
	handle->size = offset & ((PAGE_SIZE << page_order(rb)) - 1);
	handle->addr = rb->data_pages[handle->page];
	handle->addr += handle->size;
	handle->size = (PAGE_SIZE << page_order(rb)) - handle->size;

	if (have_lost) {
	lost_event.header.type = PERF_RECORD_LOST;
	lost_event.header.misc = 0;
	lost_event.id = event->id;
	lost_event.lost = local_xchg(&rb->lost, 0);

	perf_output_put(handle, lost_event);
	perf_event__output_id_sample(event, handle, &sample_data);
	}

	return 0;

	fail:
	local_inc(&rb->lost);
	perf_output_put_handle(handle);
	out:
	rcu_read_unlock();

	return -ENOSPC;
	}

	unsigned int perf_output_copy(struct perf_output_handle *handle,
	const void *buf, unsigned int len)
	{
	return __output_copy(handle, buf, len);
	}

	unsigned int perf_output_skip(struct perf_output_handle *handle,
	unsigned int len)
	{
	return __output_skip(handle, NULL, len);
	}

	void perf_output_end(struct perf_output_handle *handle)
	{
	perf_output_put_handle(handle);
	rcu_read_unlock();
	}

	static void
	ring_buffer_init(struct ring_buffer *rb, long watermark, int flags)
	{
	long max_size = perf_data_size(rb);

	if (watermark)
	rb->watermark = min(max_size, watermark);

	if (!rb->watermark)
	rb->watermark = max_size / 2;

	if (flags & RING_BUFFER_WRITABLE)
	rb->overwrite = 0;
	else
	rb->overwrite = 1;

	atomic_set(&rb->refcount, 1);

	INIT_LIST_HEAD(&rb->event_list);
	spin_lock_init(&rb->event_lock);
	}

	#ifndef CONFIG_PERF_USE_VMALLOC

	/*
	* Back perf_mmap() with regular GFP_KERNEL-0 pages.
	*/

	struct page *
	perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
	{
	if (pgoff > rb->nr_pages)
	return NULL;

	if (pgoff == 0)
	return virt_to_page(rb->user_page);

	return virt_to_page(rb->data_pages[pgoff - 1]);
	}

	static void *perf_mmap_alloc_page(int cpu)
	{
	struct page *page;
	int node;

	node = (cpu == -1) ? cpu : cpu_to_node(cpu);
	page = alloc_pages_node(node, GFP_KERNEL \| __GFP_ZERO, 0);
	if (!page)
	return NULL;

	return page_address(page);
	}

	struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
	{
	struct ring_buffer *rb;
	unsigned long size;
	int i;

	size = sizeof(struct ring_buffer);
	size += nr_pages * sizeof(void *);

	rb = kzalloc(size, GFP_KERNEL);
	if (!rb)
	goto fail;

	rb->user_page = perf_mmap_alloc_page(cpu);
	if (!rb->user_page)
	goto fail_user_page;

	for (i = 0; i < nr_pages; i++) {
	rb->data_pages[i] = perf_mmap_alloc_page(cpu);
	if (!rb->data_pages[i])
	goto fail_data_pages;
	}

	rb->nr_pages = nr_pages;

	ring_buffer_init(rb, watermark, flags);

	return rb;

	fail_data_pages:
	for (i--; i >= 0; i--)
	free_page((unsigned long)rb->data_pages[i]);

	free_page((unsigned long)rb->user_page);

	fail_user_page:
	kfree(rb);

	fail:
	return NULL;
	}

	static void perf_mmap_free_page(unsigned long addr)
	{
	struct page page = virt_to_page((void )addr);

	page->mapping = NULL;
	__free_page(page);
	}

	void rb_free(struct ring_buffer *rb)
	{
	int i;

	perf_mmap_free_page((unsigned long)rb->user_page);
	for (i = 0; i < rb->nr_pages; i++)
	perf_mmap_free_page((unsigned long)rb->data_pages[i]);
	kfree(rb);
	}

	#else
	static int data_page_nr(struct ring_buffer *rb)
	{
	return rb->nr_pages << page_order(rb);
	}

	struct page *
	perf_mmap_to_page(struct ring_buffer *rb, unsigned long pgoff)
	{
	/* The '>' counts in the user page. */
	if (pgoff > data_page_nr(rb))
	return NULL;

	return vmalloc_to_page((void )rb->user_page + pgoff PAGE_SIZE);
	}

	static void perf_mmap_unmark_page(void *addr)
	{
	struct page *page = vmalloc_to_page(addr);

	page->mapping = NULL;
	}

	static void rb_free_work(struct work_struct *work)
	{
	struct ring_buffer *rb;
	void *base;
	int i, nr;

	rb = container_of(work, struct ring_buffer, work);
	nr = data_page_nr(rb);

	base = rb->user_page;
	/* The '<=' counts in the user page. */
	for (i = 0; i <= nr; i++)
	perf_mmap_unmark_page(base + (i * PAGE_SIZE));

	vfree(base);
	kfree(rb);
	}

	void rb_free(struct ring_buffer *rb)
	{
	schedule_work(&rb->work);
	}

	struct ring_buffer *rb_alloc(int nr_pages, long watermark, int cpu, int flags)
	{
	struct ring_buffer *rb;
	unsigned long size;
	void *all_buf;

	size = sizeof(struct ring_buffer);
	size += sizeof(void *);

	rb = kzalloc(size, GFP_KERNEL);
	if (!rb)
	goto fail;

	INIT_WORK(&rb->work, rb_free_work);

	all_buf = vmalloc_user((nr_pages + 1) * PAGE_SIZE);
	if (!all_buf)
	goto fail_all_buf;

	rb->user_page = all_buf;
	rb->data_pages[0] = all_buf + PAGE_SIZE;
	rb->page_order = ilog2(nr_pages);
	rb->nr_pages = !!nr_pages;

	ring_buffer_init(rb, watermark, flags);

	return rb;

	fail_all_buf:
	kfree(rb);

	fail:
	return NULL;
	}

	#endif