[tip:core/urgent] watchdog/hardlockup/perf: Simplify deferred event destroy

[tip-bot for Thomas Gleixner]

Commit-ID:  a33d44843d4574ec05bec39527d8a87b7af2072c
Gitweb:     http://git.kernel.org/tip/a33d44843d4574ec05bec39527d8a87b7af2072c
Author:     Thomas Gleixner <tglx@xxxxxxxxxxxxx>
AuthorDate: Tue, 12 Sep 2017 21:37:22 +0200
Committer:  Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Thu, 14 Sep 2017 11:41:08 +0200

watchdog/hardlockup/perf: Simplify deferred event destroy

Now that all functionality is properly serialized against CPU hotplug,
remove the extra per cpu storage which holds the disabled events for
cleanup. The core makes sure that cleanup happens before new events are
created.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Reviewed-by: Don Zickus <dzickus@xxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Chris Metcalf <cmetcalf@xxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Nicholas Piggin <npiggin@xxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Sebastian Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Ulrich Obergfell <uobergfe@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/20170912194148.340708074@xxxxxxxxxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/watchdog_hld.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/kernel/watchdog_hld.c b/kernel/watchdog_hld.c
index 509bb6b..b293115 100644
--- a/kernel/watchdog_hld.c
+++ b/kernel/watchdog_hld.c
@@ -21,7 +21,6 @@
 static DEFINE_PER_CPU(bool, hard_watchdog_warn);
 static DEFINE_PER_CPU(bool, watchdog_nmi_touch);
 static DEFINE_PER_CPU(struct perf_event *, watchdog_ev);
-static DEFINE_PER_CPU(struct perf_event *, dead_event);
 static struct cpumask dead_events_mask;
 
 static unsigned long hardlockup_allcpu_dumped;
@@ -204,8 +203,6 @@ void hardlockup_detector_perf_disable(void)
 
 	if (event) {
 		perf_event_disable(event);
-		this_cpu_write(watchdog_ev, NULL);
-		this_cpu_write(dead_event, event);
 		cpumask_set_cpu(smp_processor_id(), &dead_events_mask);
 		watchdog_cpus--;
 	}
@@ -221,9 +218,9 @@ void hardlockup_detector_perf_cleanup(void)
 	int cpu;
 
 	for_each_cpu(cpu, &dead_events_mask) {
-		struct perf_event *event = per_cpu(dead_event, cpu);
+		struct perf_event *event = per_cpu(watchdog_ev, cpu);
 
-		per_cpu(dead_event, cpu) = NULL;
+		per_cpu(watchdog_ev, cpu) = NULL;
 		perf_event_release_kernel(event);
 	}
 	cpumask_clear(&dead_events_mask);