Messages in this thread Patch in this message | | | Date | Tue, 21 Apr 2009 14:03:29 GMT | From | tip-bot for Steven Rostedt <> | Subject | [tip:tracing/core] ring-buffer: only warn on wrap if buffer is bigger than two pages |
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Commit-ID: 3554228d4289098a8fe5cfd87512ec32a19bbe5a Gitweb: http://git.kernel.org/tip/3554228d4289098a8fe5cfd87512ec32a19bbe5a Author: Steven Rostedt <srostedt@redhat.com> AuthorDate: Tue, 21 Apr 2009 09:41:26 -0400 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Tue, 21 Apr 2009 16:00:45 +0200
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>
--- kernel/trace/ring_buffer.c | 3 ++- 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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