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Commit 6f3b3440 authored by Lai Jiangshan's avatar Lai Jiangshan Committed by Ingo Molnar
Browse files

ring_buffer: reset write when reserve buffer fail 



Impact: reset struct buffer_page.write when interrupt storm

if struct buffer_page.write is not reset, any succedent committing
will corrupted ring_buffer:

static inline void
rb_set_commit_to_write(struct ring_buffer_per_cpu *cpu_buffer)
{
	......
		cpu_buffer->commit_page->commit =
			cpu_buffer->commit_page->write;
	......
}

when "if (RB_WARN_ON(cpu_buffer, next_page == reader_page))", ring_buffer
is disabled, but some reserved buffers may haven't been committed.
we need reset struct buffer_page.write.

when "if (unlikely(next_page == cpu_buffer->commit_page))", ring_buffer
is still available, we should not corrupt it.

Signed-off-by: default avatarLai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: default avatarSteven Rostedt <srostedt@redhat.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 428aee14

kernel/trace/ring_buffer.c

+5 −5
Original line number Original line Diff line number Diff line
@@ -1017,12 +1017,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, 
		}

		}





		if (next_page == head_page) {

		if (next_page == head_page) {

			if (!(buffer->flags & RB_FL_OVERWRITE)) {

			if (!(buffer->flags & RB_FL_OVERWRITE))

				/* reset write */

				if (tail <= BUF_PAGE_SIZE)

					local_set(&tail_page->write, tail);

				goto out_unlock;

				goto out_unlock;

			}





			/* tail_page has not moved yet? */

			/* tail_page has not moved yet? */

			if (tail_page == cpu_buffer->tail_page) {

			if (tail_page == cpu_buffer->tail_page) {
@@ -1097,6 +1093,10 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer, 
	return event;

	return event;





 out_unlock:

 out_unlock:

	/* reset write */

	if (tail <= BUF_PAGE_SIZE)

		local_set(&tail_page->write, tail);



	__raw_spin_unlock(&cpu_buffer->lock);

	__raw_spin_unlock(&cpu_buffer->lock);

	local_irq_restore(flags);

	local_irq_restore(flags);

	return NULL;

	return NULL;