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authorSteven Rostedt <srostedt@redhat.com>2009-04-21 09:41:26 -0400
committerIngo Molnar <mingo@elte.hu>2009-04-21 16:00:45 +0200
commit3554228d4289098a8fe5cfd87512ec32a19bbe5a (patch)
tree6153783ba611e8d55eb4f6dde08526ee733cfb4a /kernel/trace/ring_buffer.c
parentf66578a7637b87810cbb9041c4e3a77fd2fa4706 (diff)
downloadop-kernel-dev-3554228d4289098a8fe5cfd87512ec32a19bbe5a.zip
op-kernel-dev-3554228d4289098a8fe5cfd87512ec32a19bbe5a.tar.gz
ring-buffer: only warn on wrap if buffer is bigger than two pages
On boot up, to save memory, ftrace allocates the minimum buffer which is two pages. Ftrace also goes through a series of tests (when configured) on boot up. These tests can fill up a page within a single interrupt. The ring buffer also has a WARN_ON when it detects that the buffer was completely filled within a single commit (other commits are allowed to be nested). Combine the small buffer on start up, with the tests that can fill more than a single page within an interrupt, this can trigger the WARN_ON. This patch makes the WARN_ON only happen when the ring buffer consists of more than two pages. [ Impact: prevent false WARN_ON in ftrace startup tests ] Reported-by: Ingo Molnar <mingo@elte.hu> LKML-Reference: <20090421094616.GA14561@elte.hu> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'kernel/trace/ring_buffer.c')
-rw-r--r--kernel/trace/ring_buffer.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
index 7bcfd3e..61dbdf2 100644
--- a/kernel/trace/ring_buffer.c
+++ b/kernel/trace/ring_buffer.c
@@ -1241,7 +1241,8 @@ __rb_reserve_next(struct ring_buffer_per_cpu *cpu_buffer,
* about it.
*/
if (unlikely(next_page == commit_page)) {
- WARN_ON_ONCE(1);
+ /* This can easily happen on small ring buffers */
+ WARN_ON_ONCE(buffer->pages > 2);
goto out_reset;
}
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