diff options
| author | Peter Zijlstra <peterz@infradead.org> | 2016-03-08 17:56:05 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-03-21 09:35:29 +0100 |
| commit | 1dcaac1ce07db672e2cb5b4ef9642990689bb2a1 (patch) | |
| tree | 6390f9647b7382631ba387342b53a97bb7ba11cb | |
| parent | f8519155b4d5224e215203bf0e94a8478a8f8945 (diff) | |
perf/core: Document some hotplug bits
Document some of the hotplug notifier usage.
Requested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Brian Gerst <brgerst@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Denys Vlasenko <dvlasenk@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Namhyung Kim <namhyung@kernel.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>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
| -rw-r--r-- | kernel/events/core.c | 19 |
1 files changed, 19 insertions, 0 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 43e35faf576e..de24fbce5277 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -9449,10 +9449,29 @@ perf_cpu_notify(struct notifier_block *self, unsigned long action, void *hcpu) switch (action & ~CPU_TASKS_FROZEN) { case CPU_UP_PREPARE: + /* + * This must be done before the CPU comes alive, because the + * moment we can run tasks we can encounter (software) events. + * + * Specifically, someone can have inherited events on kthreadd + * or a pre-existing worker thread that gets re-bound. + */ perf_event_init_cpu(cpu); break; case CPU_DOWN_PREPARE: + /* + * This must be done before the CPU dies because after that an + * active event might want to IPI the CPU and that'll not work + * so great for dead CPUs. + * + * XXX smp_call_function_single() return -ENXIO without a warn + * so we could possibly deal with this. + * + * This is safe against new events arriving because + * sys_perf_event_open() serializes against hotplug using + * get_online_cpus(). + */ perf_event_exit_cpu(cpu); break; default: |