Messages in this thread Patch in this message | | | From | Tan Xiaojun <> | Subject | [PATCH -stable 4.1 2/4] perf/core: Fix implicitly enable dynamic interrupt throttle | Date | Mon, 6 Mar 2017 15:14:23 +0800 |
| |
From: Kan Liang <kan.liang@intel.com>
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> Signed-off-by: Tan Xiaojun <tanxiaojun@huawei.com> --- kernel/events/core.c | 7 +++++++ 1 file changed, 7 insertions(+)
diff --git a/kernel/events/core.c b/kernel/events/core.c index 3089a004..f96ad76 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -216,6 +216,13 @@ int perf_proc_update_handler(struct ctl_table *table, int write, if (ret || !write) return ret; + /* + * If throttling is disabled don't allow the write: + */ + if (sysctl_perf_cpu_time_max_percent == 100 || + sysctl_perf_cpu_time_max_percent == 0) + return -EINVAL; + max_samples_per_tick = DIV_ROUND_UP(sysctl_perf_event_sample_rate, HZ); perf_sample_period_ns = NSEC_PER_SEC / sysctl_perf_event_sample_rate; update_perf_cpu_limits(); -- 1.9.1
| |