Re: [PATCH 1/3] Tracepoint: fix documentation of RCU lockdep checks

[Steven Rostedt]

On Mon,  2 Nov 2015 17:42:42 -0500
Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote:

> The documentation on top of __DECLARE_TRACE() does not match its
> implementation since the condition check has been added to the
> RCU lockdep checks. Update the documentation to match its
> implementation.
> 

Thanks, I can pull this now for 4.4.

-- Steve

> Fixes: a05d59a56733 "tracing: Add condition check to RCU lockdep checks"
> Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
> CC: Dave Hansen <dave@xxxxxxxx>
> CC: Steven Rostedt <rostedt@xxxxxxxxxxx>
> ---
>  include/linux/tracepoint.h | 9 +++++----
>  1 file changed, 5 insertions(+), 4 deletions(-)
> 
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index a5f7f3e..c8e3030 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -167,10 +167,11 @@ extern void syscall_unregfunc(void);
>   * structure. Force alignment to the same alignment as the section start.
>   *
>   * When lockdep is enabled, we make sure to always do the RCU portions of
> - * the tracepoint code, regardless of whether tracing is on or we match the
> - * condition.  This lets us find RCU issues triggered with tracepoints even
> - * when this tracepoint is off.  This code has no purpose other than poking
> - * RCU a bit.
> + * the tracepoint code, regardless of whether tracing is on. However,
> + * don't check if the condition is false, due to interaction with idle
> + * instrumentation. This lets us find RCU issues triggered with tracepoints
> + * even when this tracepoint is off. This code has no purpose other than
> + * poking RCU a bit.
>   */
>  #define __DECLARE_TRACE(name, proto, args, cond, data_proto, data_args) \
>  	extern struct tracepoint __tracepoint_##name;			\

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