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

[Andrew Morton <akpm@linux-foundation.org>]

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.