Re: [PATCH 4/4] ring-buffer: change WARN_ON from checking preempt_count to preemptible

Andrew Morton
2009-05-08T04:56:32Z

On Fri, 08 May 2009 00:32:54 -0400 Steven Rostedt <rostedt@goodmis.org> wrote:

> From: Steven Rostedt <srostedt@redhat.com>
>
> There's a WARN_ON in the ring buffer code that makes sure preemption
> is disabled. It checks "!preempt_count()". But when CONFIG_PREEMPT is not
> enabled, preempt_count() is always zero, and this will trigger the warning.
>
> [ Impact: prevent false warning on non preemptible kernels ]
>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> kernel/trace/ring_buffer.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c
> index 3ae5ccf..3611706 100644
> --- a/kernel/trace/ring_buffer.c
> +++ b/kernel/trace/ring_buffer.c
> @@ -1688,7 +1688,7 @@ void ring_buffer_discard_commit(struct ring_buffer *buffer,
> * committed yet. Thus we can assume that preemption
> * is still disabled.
> */
> - RB_WARN_ON(buffer, !preempt_count());
> + RB_WARN_ON(buffer, preemptible());
>
> cpu = smp_processor_id();
> cpu_buffer = buffer->buffers[cpu];

smp_processor_id() will warn too.