[tip:smp/hotplug] perf: Avoid cpu_hotplug_lock r-r recursion

["tip-bot for Peter Zijlstra (Intel)" <tipbot@zytor.com>]

Commit-ID:  641693094ee1568502280f95900f374b2226b51d
Gitweb:     http://git.kernel.org/tip/641693094ee1568502280f95900f374b2226b51d
Author:     Peter Zijlstra (Intel) <peterz@infradead.org>
AuthorDate: Tue, 18 Apr 2017 19:05:05 +0200
Committer:  Thomas Gleixner <tglx@linutronix.de>
CommitDate: Thu, 20 Apr 2017 13:08:57 +0200

perf: Avoid cpu_hotplug_lock r-r recursion

There are two call-sites where using static_key results in recursing on the
cpu_hotplug_lock.

Use the hotplug locked version of static_key_slow_inc().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Sebastian Siewior <bigeasy@linutronix.de>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: jbaron@akamai.com
Link: http://lkml.kernel.org/r/20170418103422.687248115@infradead.org

---
 kernel/events/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 634dd95..8aa3063 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7653,7 +7653,7 @@ static int perf_swevent_init(struct perf_event *event)
 		if (err)
 			return err;
 
-		static_key_slow_inc(&perf_swevent_enabled[event_id]);
+		static_key_slow_inc_cpuslocked(&perf_swevent_enabled[event_id]);
 		event->destroy = sw_perf_event_destroy;
 	}
 
@@ -9160,7 +9160,7 @@ static void account_event(struct perf_event *event)
 
 		mutex_lock(&perf_sched_mutex);
 		if (!atomic_read(&perf_sched_count)) {
-			static_branch_enable(&perf_sched_events);
+			static_key_slow_inc_cpuslocked(&perf_sched_events.key);
 			/*
 			 * Guarantee that all CPUs observe they key change and
 			 * call the perf scheduling hooks before proceeding to