kernel/events/ring_buffer.c - third_party/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 <linux/circ_buf.h>

 #include "internal.h"

 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;

 	/*
 	 * Since the mmap() consumer (userspace) can run on a different CPU:
 	 *
 	 *   kernel				user
 	 *
 	 *   if (LOAD ->data_tail) {		LOAD ->data_head
 	 *			(A)		smp_rmb()	(C)
 	 *	STORE $data			LOAD $data
 	 *	smp_wmb()	(B)		smp_mb()	(D)
 	 *	STORE ->data_head		STORE ->data_tail
 	 *   }
 	 *
 	 * Where A pairs with D, and B pairs with C.
 	 *
 	 * In our case (A) is a control dependency that separates the load of
 	 * the ->data_tail and the stores of $data. In case ->data_tail
 	 * indicates there is no room in the buffer to store $data we do not.
 	 *
 	 * D needs to be a full barrier since it separates the data READ
 	 * from the tail WRITE.
 	 *
 	 * For B a WMB is sufficient since it separates two WRITEs, and for C
 	 * an RMB is sufficient since it separates two READs.
 	 *
 	 * See perf_output_begin().
 	 */
 	smp_wmb(); /* B, matches C */
 	rb->user_page->data_head = head;

 	/*
 	 * Now check if we missed an update -- rely on previous implied
 	 * compiler barriers to force a re-read.
 	 */
 	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, page_shift;
 	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 (unlikely(!rb))
 		goto out;

 	if (unlikely(!rb->nr_pages))
 		goto out;

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

 	have_lost = local_read(&rb->lost);
 	if (unlikely(have_lost)) {
 		size += sizeof(lost_event);
 		if (event->attr.sample_id_all)
 			size += event->id_header_size;
 	}

 	perf_output_get_handle(handle);

 	do {
 		tail = ACCESS_ONCE(rb->user_page->data_tail);
 		offset = head = local_read(&rb->head);
 		if (!rb->overwrite &&
 		    unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))
 			goto fail;

 		/*
 		 * The above forms a control dependency barrier separating the
 		 * @tail load above from the data stores below. Since the @tail
 		 * load is required to compute the branch to fail below.
 		 *
 		 * A, matches D; the full memory barrier userspace SHOULD issue
 		 * after reading the data and before storing the new tail
 		 * position.
 		 *
 		 * See perf_output_put_handle().
 		 */

 		head += size;
 	} while (local_cmpxchg(&rb->head, offset, head) != offset);

 	/*
 	 * We rely on the implied barrier() by local_cmpxchg() to ensure
 	 * none of the data stores below can be lifted up by the compiler.
 	 */

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

 	page_shift = PAGE_SHIFT + page_order(rb);

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

 	if (unlikely(have_lost)) {
 		struct perf_sample_data sample_data;

 		lost_event.header.size = sizeof(lost_event);
 		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_event_header__init_id(&lost_event.header,
 					   &sample_data, event);
 		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 <linux/circ_buf.h>

	#include "internal.h"

	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;

	/*
	* Since the mmap() consumer (userspace) can run on a different CPU:
	*
	* kernel user
	*
	* if (LOAD ->data_tail) { LOAD ->data_head
	* (A) smp_rmb() (C)
	* STORE $data LOAD $data
	* smp_wmb() (B) smp_mb() (D)
	* STORE ->data_head STORE ->data_tail
	* }
	*
	* Where A pairs with D, and B pairs with C.
	*
	* In our case (A) is a control dependency that separates the load of
	* the ->data_tail and the stores of $data. In case ->data_tail
	* indicates there is no room in the buffer to store $data we do not.
	*
	* D needs to be a full barrier since it separates the data READ
	* from the tail WRITE.
	*
	* For B a WMB is sufficient since it separates two WRITEs, and for C
	* an RMB is sufficient since it separates two READs.
	*
	* See perf_output_begin().
	*/
	smp_wmb(); /* B, matches C */
	rb->user_page->data_head = head;

	/*
	* Now check if we missed an update -- rely on previous implied
	* compiler barriers to force a re-read.
	*/
	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, page_shift;
	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 (unlikely(!rb))
	goto out;

	if (unlikely(!rb->nr_pages))
	goto out;

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

	have_lost = local_read(&rb->lost);
	if (unlikely(have_lost)) {
	size += sizeof(lost_event);
	if (event->attr.sample_id_all)
	size += event->id_header_size;
	}

	perf_output_get_handle(handle);

	do {
	tail = ACCESS_ONCE(rb->user_page->data_tail);
	offset = head = local_read(&rb->head);
	if (!rb->overwrite &&
	unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size))
	goto fail;

	/*
	* The above forms a control dependency barrier separating the
	* @tail load above from the data stores below. Since the @tail
	* load is required to compute the branch to fail below.
	*
	* A, matches D; the full memory barrier userspace SHOULD issue
	* after reading the data and before storing the new tail
	* position.
	*
	* See perf_output_put_handle().
	*/

	head += size;
	} while (local_cmpxchg(&rb->head, offset, head) != offset);

	/*
	* We rely on the implied barrier() by local_cmpxchg() to ensure
	* none of the data stores below can be lifted up by the compiler.
	*/

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

	page_shift = PAGE_SHIFT + page_order(rb);

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

	if (unlikely(have_lost)) {
	struct perf_sample_data sample_data;

	lost_event.header.size = sizeof(lost_event);
	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_event_header__init_id(&lost_event.header,
	&sample_data, event);
	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