From 3554228d4289098a8fe5cfd87512ec32a19bbe5a Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Tue, 21 Apr 2009 09:41:26 -0400 Subject: 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 LKML-Reference: <20090421094616.GA14561@elte.hu> Signed-off-by: Steven Rostedt Signed-off-by: Ingo Molnar --- kernel/trace/ring_buffer.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 7bcfd3e60537..61dbdf21cd32 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; } -- cgit v1.2.3