Re: [PATCH] ring_buffer: reset write when reserve buffer fail
From: Steven Rostedt
Date: Wed Jan 14 2009 - 13:19:54 EST
Hi Lai,
Sorry for the late response, I've got a million things going on at once,
and this needed more thought than a quick review.
On Mon, 12 Jan 2009, Lai Jiangshan wrote:
>
> 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.
So what you are saying is, when we hit this anomaly, another cpu might be
writing to the ring buffer, and will soon do a commit.
>
> when "if (unlikely(next_page == cpu_buffer->commit_page))", ring_buffer
> is still available, we should not corrupt it.
OK, makes sense. I'll queue it up.
Thanks!
-- Steve
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