perf/core: Fix implicitly enable dynamic interrupt throttle
authorKan Liang <kan.liang@intel.com>
Tue, 3 May 2016 07:26:06 +0000 (00:26 -0700)
committerIngo Molnar <mingo@kernel.org>
Fri, 3 Jun 2016 07:40:16 +0000 (09:40 +0200)
commitab7fdefba68f66c8523571c3b3a940635d781824
tree36c28f0292b06116e6ed4d3cdd35dfc58b173492
parentaab5b71ef2b5c62323b9abe397e2db57b18e1f78
perf/core: Fix implicitly enable dynamic interrupt throttle

This patch fixes an issue which was introduced by commit:

  91a612eea9a3 ("perf/core: Fix dynamic interrupt throttle")

... which commit unconditionally sets the perf_sample_allowed_ns value
to !0. But that could trigger a bug in the following corner case:

The user can disable the dynamic interrupt throttle mechanism by setting
perf_cpu_time_max_percent to 0. Then they change perf_event_max_sample_rate.
For this case, the mechanism will be enabled implicitly, because
perf_sample_allowed_ns becomes !0 - which is not what we want.

This patch only updates perf_sample_allowed_ns when the dynamic
interrupt throttle mechanism is enabled.

Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Link: http://lkml.kernel.org/r/1462260366-3160-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
kernel/events/core.c