Commit 1dcaac1c authored Mar 08, 2016 by Peter Zijlstra Committed by Ingo Molnar Mar 21, 2016

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>

parent f8519155

kernel/events/core.c

+19 −0

Original line number	Diff line number	Diff line
		@@ -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: