linux-kernel - [PATCH] ring_buffer: map to cpu not page

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Date:	Thu, 2 Oct 2008 19:18:09 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ingo Molnar <mingo@...e.hu>
cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Jonathan Corbet <corbet@....net>,
	Mathieu Desnoyers <compudj@...stal.dyndns.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	prasad@...ux.vnet.ibm.com, "Frank Ch. Eigler" <fche@...hat.com>,
	David Wilder <dwilder@...ibm.com>, hch@....de,
	Martin Bligh <mbligh@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Steven Rostedt <srostedt@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
Subject: [PATCH] ring_buffer: map to cpu not page


My original patch had a compile bug when NUMA was configured. I
referenced cpu when it should have been cpu_buffer->cpu.

Ingo quickly fixed this bug by replacing cpu with 'i' because that
was the loop counter. Unfortunately, the 'i' was the counter of
pages, not CPUs. This caused a crash when the number of pages allocated
for the buffers exceeded the number of pages, which would usually
be the case.

Signed-off-by: Steven Rostedt <srostedt@...hat.com>
---
 kernel/trace/ring_buffer.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-tip.git/kernel/trace/ring_buffer.c
===================================================================
--- linux-tip.git.orig/kernel/trace/ring_buffer.c	2008-10-02 09:09:01.000000000 -0400
+++ linux-tip.git/kernel/trace/ring_buffer.c	2008-10-02 18:58:44.000000000 -0400
@@ -232,7 +232,7 @@ static int rb_allocate_pages(struct ring
 
 	for (i = 0; i < nr_pages; i++) {
 		page = kzalloc_node(ALIGN(sizeof(*page), cache_line_size()),
-				    GFP_KERNEL, cpu_to_node(i));
+				    GFP_KERNEL, cpu_to_node(cpu_buffer->cpu));
 		if (!page)
 			goto free_pages;
 		list_add(&page->list, &pages);


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