On Mon, Mar 14, 2016 at 02:16:44PM +0100, Jiri Slaby wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>
>
> This patch has been added to the 3.12 stable tree. If you have any
> objections, please let us know.
>
Please note that this patch was tagged for stable 3.18+.
Cheers,
--
Luís
> ===============
>
> 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@xxxxxxx>
> Tested-by: Sudeep Holla <sudeep.holla@xxxxxxx>
> Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
> ---
> include/linux/tracepoint.h | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/tracepoint.h b/include/linux/tracepoint.h
> index c1248996006f..9ff9ca22cfb7 100644
> --- a/include/linux/tracepoint.h
> +++ b/include/linux/tracepoint.h
> @@ -129,9 +129,6 @@ static inline void tracepoint_synchronize_unregister(void)
> 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_synchronize_unregister(void)
> * "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))
>
> --
> 2.7.3
>
> --
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