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[PATCH] perf/core: Remove redundant get_online_cpus()

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  [PATCH] perf/core: Remove redundant get_online_cpus() Thomas Gleixner <tglx@linutronix.de> - 2017-04-17 11:20 +0200

#1624613 — [PATCH] perf/core: Remove redundant get_online_cpus()

SyS_perf_event_open() calls get_online_cpus() and eventually invokes
swevent_hlist_get() which does it again. 

All callchains leading to swevent_hlist_get() originate from
SyS_perf_event_open() so the extra protection is redundant.

Remove it.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Peter Zijlstra <peterz@infradead.org>
---
 kernel/events/core.c |    5 -----
 1 file changed, 5 deletions(-)

--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -7592,7 +7592,6 @@ static int swevent_hlist_get(void)
 {
 	int err, cpu, failed_cpu;
 
-	get_online_cpus();
 	for_each_possible_cpu(cpu) {
 		err = swevent_hlist_get_cpu(cpu);
 		if (err) {
@@ -7600,8 +7599,6 @@ static int swevent_hlist_get(void)
 			goto fail;
 		}
 	}
-	put_online_cpus();
-
 	return 0;
 fail:
 	for_each_possible_cpu(cpu) {
@@ -7609,8 +7606,6 @@ static int swevent_hlist_get(void)
 			break;
 		swevent_hlist_put_cpu(cpu);
 	}
-
-	put_online_cpus();
 	return err;
 }
 

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