[PATCH 7.2.y 2/3] s390/pai: Move locking to event init and delete

[Sasha Levin <sashal@kernel.org>]

From: Thomas Richter <tmricht@linux.ibm.com>

[ Upstream commit e8df39dacb7d98d2b2aea431ca652d9fadf5efa3 ]

Move mutex locking from per CPU allocation to event allocation.
No functional change.

Signed-off-by: Thomas Richter <tmricht@linux.ibm.com>
Reviewed-by: Sumanth Korikkar <sumanthk@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Vasily Gorbik <gor@linux.ibm.com>
Stable-dep-of: 9ecc4d033879 ("s390/pai: Support CPU hotplug for PMU PAI")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/s390/kernel/perf_pai.c | 25 ++++++++++++-------------
 1 file changed, 12 insertions(+), 13 deletions(-)

diff --git a/arch/s390/kernel/perf_pai.c b/arch/s390/kernel/perf_pai.c
index 7c13f5586c793..52d9f654346a2 100644
--- a/arch/s390/kernel/perf_pai.c
+++ b/arch/s390/kernel/perf_pai.c
@@ -138,21 +138,19 @@ static void pai_free(struct pai_mapptr *mp)
 }
 
 /* Adjust usage counters and remove allocated memory when all users are
- * gone.
+ * gone. Called under mutex_lock.
  */
 static void pai_event_destroy_cpu(int idx, int cpu)
 {
 	struct pai_mapptr *mp = per_cpu_ptr(pai_root[idx].mapptr, cpu);
 	struct pai_map *cpump = mp->mapptr;
 
-	mutex_lock(&pai_reserve_mutex);
 	debug_sprintf_event(paidbg, 5, "%s users %d refcnt %u\n",
 			    __func__, cpump->active_events,
 			    refcount_read(&cpump->refcnt));
 	if (refcount_dec_and_test(&cpump->refcnt))
 		pai_free(mp);
 	pai_root_free(idx);
-	mutex_unlock(&pai_reserve_mutex);
 }
 
 static void pai_event_destroy(struct perf_event *event)
@@ -160,6 +158,7 @@ static void pai_event_destroy(struct perf_event *event)
 	int cpu = 0, idx = PAI_PMU_IDX(event);
 
 	free_page(PAI_SAVE_AREA(event));
+	mutex_lock(&pai_reserve_mutex);
 	if (event->cpu == -1) {
 		struct cpumask *mask = PAI_CPU_MASK(event);
 
@@ -169,6 +168,7 @@ static void pai_event_destroy(struct perf_event *event)
 	} else {
 		pai_event_destroy_cpu(idx, event->cpu);
 	}
+	mutex_unlock(&pai_reserve_mutex);
 }
 
 static void paicrypt_event_destroy(struct perf_event *event)
@@ -232,12 +232,10 @@ static u64 paicrypt_getall(struct perf_event *event)
 	return sum;
 }
 
-/* Check concurrent access of counting and sampling for crypto events.
- * This function is called in process context and it is save to block.
- * When the event initialization functions fails, no other call back will
- * be invoked.
- *
- * Allocate the memory for the event.
+/* Allocate all per-CPU data structures. This function is called in
+ * process context and can block. In case of error all partly allocated
+ * memory is released and the reference counters adjusted correctly.
+ * Called under mutex_lock.
  */
 static int pai_alloc_cpu(int idx, int cpu)
 {
@@ -246,11 +244,10 @@ static int pai_alloc_cpu(int idx, int cpu)
 	struct pai_mapptr *mp;
 	int rc;
 
-	mutex_lock(&pai_reserve_mutex);
 	/* Allocate root node */
 	rc = pai_root_alloc(idx);
 	if (rc)
-		goto unlock;
+		goto out;
 
 	/* Allocate node for this event */
 	mp = per_cpu_ptr(pai_root[idx].mapptr, cpu);
@@ -308,12 +305,12 @@ static int pai_alloc_cpu(int idx, int cpu)
 		 */
 		pai_root_free(idx);
 	}
-unlock:
-	mutex_unlock(&pai_reserve_mutex);
+out:
 	/* If rc is non-zero, no increment of counter/sampler was done. */
 	return rc;
 }
 
+/* Called under mutex_lock */
 static int pai_alloc(struct perf_event *event)
 {
 	int idx = PAI_PMU_IDX(event);
@@ -390,10 +387,12 @@ static int pai_event_init(struct perf_event *event, int idx)
 		}
 	}
 
+	mutex_lock(&pai_reserve_mutex);
 	if (event->cpu >= 0)
 		rc = pai_alloc_cpu(idx, event->cpu);
 	else
 		rc = pai_alloc(event);
+	mutex_unlock(&pai_reserve_mutex);
 	if (rc) {
 		free_page(PAI_SAVE_AREA(event));
 		goto out;
-- 
2.53.0