[PATCH AUTOSEL 4.18 065/100] perf/core: Fix perf_pmu_unregister() locking

[Sasha Levin]

From: Peter Zijlstra <pet...@infradead.org>

[ Upstream commit a9f9772114c8b07ae75bcb3654bd017461248095 ]

When we unregister a PMU, we fail to serialize the @pmu_idr properly.
Fix that by doing the entire thing under pmu_lock.

Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
Cc: Alexander Shishkin <alexander.shish...@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: Jiri Olsa <jo...@redhat.com>
Cc: Linus Torvalds <torva...@linux-foundation.org>
Cc: Peter Zijlstra <pet...@infradead.org>
Cc: Stephane Eranian <eran...@google.com>
Cc: Thomas Gleixner <t...@linutronix.de>
Cc: Vince Weaver <vincent.wea...@maine.edu>
Fixes: 2e80a82a49c4 ("perf: Dynamic pmu types")
Signed-off-by: Ingo Molnar <mi...@kernel.org>
Signed-off-by: Sasha Levin <sas...@kernel.org>
---
 kernel/events/core.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/kernel/events/core.c b/kernel/events/core.c
index ae22d93701db..b1ed5e99d9c6 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9436,9 +9436,7 @@ static void free_pmu_context(struct pmu *pmu)
        if (pmu->task_ctx_nr > perf_invalid_context)
                return;
 
-       mutex_lock(&pmus_lock);
        free_percpu(pmu->pmu_cpu_context);
-       mutex_unlock(&pmus_lock);
 }
 
 /*
@@ -9694,12 +9692,8 @@ EXPORT_SYMBOL_GPL(perf_pmu_register);
 
 void perf_pmu_unregister(struct pmu *pmu)
 {
-       int remove_device;
-
        mutex_lock(&pmus_lock);
-       remove_device = pmu_bus_running;
        list_del_rcu(&pmu->entry);
-       mutex_unlock(&pmus_lock);
 
        /*
         * We dereference the pmu list under both SRCU and regular RCU, so
@@ -9711,13 +9705,14 @@ void perf_pmu_unregister(struct pmu *pmu)
        free_percpu(pmu->pmu_disable_count);
        if (pmu->type >= PERF_TYPE_MAX)
                idr_remove(&pmu_idr, pmu->type);
-       if (remove_device) {
+       if (pmu_bus_running) {
                if (pmu->nr_addr_filters)
                        device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
                device_del(pmu->dev);
                put_device(pmu->dev);
        }
        free_pmu_context(pmu);
+       mutex_unlock(&pmus_lock);
 }
 EXPORT_SYMBOL_GPL(perf_pmu_unregister);
 
-- 
2.17.1