From 19de2ea4b733604ba0e6a8933b396350f0339346 Mon Sep 17 00:00:00 2001 From: Kan Liang Date: Mon, 6 Mar 2017 15:14:23 +0800 Subject: 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Alexander Shishkin Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver 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 Signed-off-by: Tan Xiaojun Signed-off-by: Sasha Levin --- kernel/events/core.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/kernel/events/core.c b/kernel/events/core.c index fb5f6f459aff..338362db17d1 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(); -- cgit v1.2.3