From: Lai Jiangshan <laijs@cn.fujitsu.com>
Date: Mon, 12 Jan 2009 03:06:18 +0000 (+0800)
Subject: ring_buffer: reset write when reserve buffer fail
X-Git-Tag: v2.6.29-rc4~81^2~5
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=551b4048b3d4acf15aff9fe4aed89b892c135b02;p=pandora-kernel.git

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: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---

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