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perf/core: Fix perf_pmu_unregister() locking 

commit a9f9772114c8b07ae75bcb3654bd017461248095 upstream.

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) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 2e80a82a49 ("perf: Dynamic pmu types")
Signed-off-by: Ingo Molnar <mingo@kernel.org>
[bwh: Backported to 3.16:
 - Also remove "out" label in free_pmu_context()
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
This commit is contained in:
Peter Zijlstra 2018-09-25 17:58:35 +02:00 committed by syphyr
parent cf7f578544
commit fa34295619
1 changed files with 3 additions and 9 deletions
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12
kernel/events/core.c
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@ -6419,20 +6419,17 @@ static void free_pmu_context(struct pmu *pmu)
{
struct pmu *i;
mutex_lock(&pmus_lock);
/*
* Like a real lame refcount.
*/
list_for_each_entry(i, &pmus, entry) {
if (i->pmu_cpu_context == pmu->pmu_cpu_context) {
update_pmu_context(i, pmu);
goto out;
return;
}
}
free_percpu(pmu->pmu_cpu_context);
out:
mutex_unlock(&pmus_lock);
}
static struct idr pmu_idr;
@ -6593,12 +6590,8 @@ free_pdc:
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
@ -6610,11 +6603,12 @@ 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) {
device_del(pmu->dev);
put_device(pmu->dev);
}
free_pmu_context(pmu);
mutex_unlock(&pmus_lock);
}
struct pmu *perf_init_event(struct perf_event *event)