Commit 667d2412 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Steven Rostedt
Browse files

ring_buffer: fix ring_buffer_read_page() 



Impact: change API and init bpage when copy

ring_buffer_read_page()/rb_remove_entries() may be called for
a partially consumed page.

Add a parameter for rb_remove_entries() and make it update
cpu_buffer->entries correctly for partially consumed pages.

ring_buffer_read_page() now returns the offset to the next event.

Init the bpage's time_stamp when return value is 0.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
parent b85fa01e

kernel/trace/ring_buffer.c

+20 −13
Original line number Diff line number Diff line
@@ -2332,13 +2332,14 @@ int ring_buffer_swap_cpu(struct ring_buffer *buffer_a, 
EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu);



static void rb_remove_entries(struct ring_buffer_per_cpu *cpu_buffer,

			      struct buffer_data_page *bpage)

			      struct buffer_data_page *bpage,

			      unsigned int offset)

{

	struct ring_buffer_event *event;

	unsigned long head;



	__raw_spin_lock(&cpu_buffer->lock);

	for (head = 0; head < local_read(&bpage->commit);

	for (head = offset; head < local_read(&bpage->commit);

	     head += rb_event_length(event)) {



		event = __rb_data_page_index(bpage, head);
@@ -2410,8 +2411,8 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) 
 *	if (!rpage)

 *		return error;

 *	ret = ring_buffer_read_page(buffer, &rpage, cpu, 0);

 *	if (ret)

 *		process_page(rpage);

 *	if (ret >= 0)

 *		process_page(rpage, ret);

 *

 * When @full is set, the function will not return true unless

 * the writer is off the reader page.
@@ -2422,8 +2423,8 @@ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) 
 *  responsible for that.

 *

 * Returns:

 *  1 if data has been transferred

 *  0 if no data has been transferred.

 *  >=0 if data has been transferred, returns the offset of consumed data.

 *  <0 if no data has been transferred.

 */

int ring_buffer_read_page(struct ring_buffer *buffer,

			    void **data_page, int cpu, int full)
@@ -2432,7 +2433,8 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
	struct ring_buffer_event *event;

	struct buffer_data_page *bpage;

	unsigned long flags;

	int ret = 0;

	unsigned int read;

	int ret = -1;



	if (!data_page)

		return 0;
@@ -2454,24 +2456,29 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
	/* check for data */

	if (!local_read(&cpu_buffer->reader_page->page->commit))

		goto out;



	read = cpu_buffer->reader_page->read;

	/*

	 * If the writer is already off of the read page, then simply

	 * switch the read page with the given page. Otherwise

	 * we need to copy the data from the reader to the writer.

	 */

	if (cpu_buffer->reader_page == cpu_buffer->commit_page) {

		unsigned int read = cpu_buffer->reader_page->read;

		unsigned int commit = rb_page_commit(cpu_buffer->reader_page);

		struct buffer_data_page *rpage = cpu_buffer->reader_page->page;



		if (full)

			goto out;

		/* The writer is still on the reader page, we must copy */

		memcpy(bpage->data,

		       cpu_buffer->reader_page->page->data + read,

		       commit - read);

		memcpy(bpage->data + read, rpage->data + read, commit - read);



		/* consume what was read */

		cpu_buffer->reader_page->read = commit;



		/* update bpage */

		local_set(&bpage->commit, commit);

		if (!read)

			bpage->time_stamp = rpage->time_stamp;

	} else {

		/* swap the pages */

		rb_init_page(bpage);
@@ -2480,10 +2487,10 @@ int ring_buffer_read_page(struct ring_buffer *buffer, 
		cpu_buffer->reader_page->read = 0;

		*data_page = bpage;

	}

	ret = 1;

	ret = read;



	/* update the entry counter */

	rb_remove_entries(cpu_buffer, bpage);

	rb_remove_entries(cpu_buffer, bpage, read);

 out:

	spin_unlock_irqrestore(&cpu_buffer->reader_lock, flags);

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