Re: Patch "tracing: Fix check for cpu online when event is disabled" has been added to the 3.10-stable tree

[Luis Henriques <luis.henriques@canonical.com>]

On Fri, Mar 11, 2016 at 11:04:00PM -0800, Greg Kroah-Hartman wrote:
> 
> This is a note to let you know that I've just added the patch titled
> 
>     tracing: Fix check for cpu online when event is disabled
> 
> to the 3.10-stable tree which can be found at:
>     http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
> 
> The filename of the patch is:
>      tracing-fix-check-for-cpu-online-when-event-is-disabled.patch
> and it can be found in the queue-3.10 subdirectory.
> 
> If you, or anyone else, feels it should not be added to the stable tree,
> please let <stable@vger.kernel.org> know about it.
>

Please note that this patch was tagged for stable 3.18+.

Cheers,
--
Lu�s


> 
> From dc17147de328a74bbdee67c1bf37d2f1992de756 Mon Sep 17 00:00:00 2001
> From: "Steven Rostedt (Red Hat)" <rostedt@goodmis.org>
> Date: Wed, 9 Mar 2016 11:58:41 -0500
> Subject: tracing: Fix check for cpu online when event is disabled
> 
> From: Steven Rostedt (Red Hat) <rostedt@goodmis.org>
> 
> commit dc17147de328a74bbdee67c1bf37d2f1992de756 upstream.
> 
> Commit f37755490fe9b ("tracepoints: Do not trace when cpu is offline") added
> a check to make sure that tracepoints only get called when the cpu is
> online, as it uses rcu_read_lock_sched() for protection.
> 
> Commit 3a630178fd5f3 ("tracing: generate RCU warnings even when tracepoints
> are disabled") added lockdep checks (including rcu checks) for events that
> are not enabled to catch possible RCU issues that would only be triggered if
> a trace event was enabled. Commit f37755490fe9b only stopped the warnings
> when the trace event was enabled but did not prevent warnings if the trace
> event was called when disabled.
> 
> To fix this, the cpu online check is moved to where the condition is added
> to the trace event. This will place the cpu online check in all places that
> it may be used now and in the future.
> 
> Fixes: f37755490fe9b ("tracepoints: Do not trace when cpu is offline")
> Fixes: 3a630178fd5f3 ("tracing: generate RCU warnings even when tracepoints are disabled")
> Reported-by: Sudeep Holla <sudeep.holla@arm.com>
> Tested-by: Sudeep Holla <sudeep.holla@arm.com>
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> 
> ---
>  include/linux/tracepoint.h |   17 +++++++++--------
>  1 file changed, 9 insertions(+), 8 deletions(-)
> 
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -129,9 +129,6 @@ static inline void tracepoint_synchroniz
>  		void *it_func;						\
>  		void *__data;						\
>  									\
> -		if (!cpu_online(raw_smp_processor_id()))		\
> -			return;						\
> -									\
>  		if (!(cond))						\
>  			return;						\
>  		prercu;							\
> @@ -265,15 +262,19 @@ static inline void tracepoint_synchroniz
>   * "void *__data, proto" as the callback prototype.
>   */
>  #define DECLARE_TRACE_NOARGS(name)					\
> -		__DECLARE_TRACE(name, void, , 1, void *__data, __data)
> +	__DECLARE_TRACE(name, void, ,					\
> +			cpu_online(raw_smp_processor_id()),		\
> +			void *__data, __data)
>  
>  #define DECLARE_TRACE(name, proto, args)				\
> -		__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), 1,	\
> -				PARAMS(void *__data, proto),		\
> -				PARAMS(__data, args))
> +	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
> +			cpu_online(raw_smp_processor_id()),		\
> +			PARAMS(void *__data, proto),			\
> +			PARAMS(__data, args))
>  
>  #define DECLARE_TRACE_CONDITION(name, proto, args, cond)		\
> -	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args), PARAMS(cond), \
> +	__DECLARE_TRACE(name, PARAMS(proto), PARAMS(args),		\
> +			cpu_online(raw_smp_processor_id()) && (PARAMS(cond)), \
>  			PARAMS(void *__data, proto),			\
>  			PARAMS(__data, args))
>  
> 
> 
> Patches currently in stable-queue which might be from rostedt@goodmis.org are
> 
> queue-3.10/tracing-fix-check-for-cpu-online-when-event-is-disabled.patch
> --
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