[tip: perf/core] perf/core: Fix unlock balance in perf_init_event()

[tip-bot2 for Qian Cai]

The following commit has been merged into the perf/core branch of tip:

Commit-ID:     deb0c3c29d552ab81ecd5481bb83bf2f4e41927d
Gitweb:        https://git.kernel.org/tip/deb0c3c29d552ab81ecd5481bb83bf2f4e41927d
Author:        Qian Cai <cai@xxxxxx>
AuthorDate:    Wed, 06 Nov 2019 00:29:35 -05:00
Committer:     Ingo Molnar <mingo@xxxxxxxxxx>
CommitterDate: Wed, 13 Nov 2019 11:06:13 +01:00

perf/core: Fix unlock balance in perf_init_event()

Commit:

  66d258c5b048 ("perf/core: Optimize perf_init_event()")

introduced an unlock imbalance in perf_init_event() where it calls
"goto again" and then only repeat rcu_read_unlock().

Signed-off-by: Qian Cai <cai@xxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
Cc: David Ahern <dsahern@xxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Mark Rutland <mark.rutland@xxxxxxx>
Cc: Namhyung Kim <namhyung@xxxxxxxxxx>
Cc: Stephane Eranian <eranian@xxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vince Weaver <vincent.weaver@xxxxxxxxx>
Fixes: 66d258c5b048 ("perf/core: Optimize perf_init_event()")
Link: https://lkml.kernel.org/r/20191106052935.8352-1-cai@xxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
 kernel/events/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index 6cb6d68..8d65e03 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -10307,7 +10307,6 @@ static struct pmu *perf_init_event(struct perf_event *event)
 			goto unlock;
 	}
 
-	rcu_read_lock();
 	/*
 	 * PERF_TYPE_HARDWARE and PERF_TYPE_HW_CACHE
 	 * are often aliases for PERF_TYPE_RAW.
@@ -10317,6 +10316,7 @@ static struct pmu *perf_init_event(struct perf_event *event)
 		type = PERF_TYPE_RAW;
 
 again:
+	rcu_read_lock();
 	pmu = idr_find(&pmu_idr, type);
 	rcu_read_unlock();
 	if (pmu) {