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Subject[PATCH 4/5] perf: Move event owner retrieval into perf_event_get_owner
Date
Moving the code of getting safely event's owner into
perf_event_get_owner function, so it could be used
in following change.

Cc: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
---
include/linux/perf_event.h | 1 +
kernel/events/core.c | 23 +++++++++++++++--------
2 files changed, 16 insertions(+), 8 deletions(-)

diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
index 707617a..ec6ef94 100644
--- a/include/linux/perf_event.h
+++ b/include/linux/perf_event.h
@@ -784,6 +784,7 @@ extern void perf_event_enable(struct perf_event *event);
extern void perf_event_disable(struct perf_event *event);
extern int __perf_event_disable(void *info);
extern void perf_event_task_tick(void);
+extern struct task_struct *perf_event_get_owner(struct perf_event *event);
#else /* !CONFIG_PERF_EVENTS: */
static inline void
perf_event_task_sched_in(struct task_struct *prev,
diff --git a/kernel/events/core.c b/kernel/events/core.c
index a36ebfe..faba9e0 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -3311,17 +3311,10 @@ static void free_event(struct perf_event *event)
_free_event(event);
}

-/*
- * Called when the last reference to the file is gone.
- */
-static void put_event(struct perf_event *event)
+struct task_struct *perf_event_get_owner(struct perf_event *event)
{
- struct perf_event_context *ctx = event->ctx;
struct task_struct *owner;

- if (!atomic_long_dec_and_test(&event->refcount))
- return;
-
rcu_read_lock();
owner = ACCESS_ONCE(event->owner);
/*
@@ -3340,7 +3333,21 @@ static void put_event(struct perf_event *event)
get_task_struct(owner);
}
rcu_read_unlock();
+ return owner;
+}
+
+/*
+ * Called when the last reference to the file is gone.
+ */
+static void put_event(struct perf_event *event)
+{
+ struct perf_event_context *ctx = event->ctx;
+ struct task_struct *owner;
+
+ if (!atomic_long_dec_and_test(&event->refcount))
+ return;

+ owner = perf_event_get_owner(event);
if (owner) {
mutex_lock(&owner->perf_event_mutex);
/*
--
1.8.3.1


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