This is a note to let you know that I've just added the patch titled
perf/core: Fix pmus_lock vs. pmus_srcu ordering
to the 6.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
perf-core-fix-pmus_lock-vs.-pmus_srcu-ordering.patch
and it can be found in the queue-6.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 2e9d0f681285b172226a8e222b8dad68111555f1
Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Date: Mon Nov 4 14:39:11 2024 +0100
perf/core: Fix pmus_lock vs. pmus_srcu ordering
[ Upstream commit 2565e42539b120b81a68a58da961ce5d1e34eac8 ]
Commit a63fbed776c7 ("perf/tracing/cpuhotplug: Fix locking order")
placed pmus_lock inside pmus_srcu, this makes perf_pmu_unregister()
trip lockdep.
Move the locking about such that only pmu_idr and pmus (list) are
modified while holding pmus_lock. This avoids doing synchronize_srcu()
while holding pmus_lock and all is well again.
Fixes: a63fbed776c7 ("perf/tracing/cpuhotplug: Fix locking order")
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20241104135517.679556858@xxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/kernel/events/core.c b/kernel/events/core.c
index a0e1d2124727e..5fff74c736063 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -11846,6 +11846,8 @@ void perf_pmu_unregister(struct pmu *pmu)
{
mutex_lock(&pmus_lock);
list_del_rcu(&pmu->entry);
+ idr_remove(&pmu_idr, pmu->type);
+ mutex_unlock(&pmus_lock);
/*
* We dereference the pmu list under both SRCU and regular RCU, so
@@ -11855,7 +11857,6 @@ void perf_pmu_unregister(struct pmu *pmu)
synchronize_rcu();
free_percpu(pmu->pmu_disable_count);
- idr_remove(&pmu_idr, pmu->type);
if (pmu_bus_running && pmu->dev && pmu->dev != PMU_NULL_DEV) {
if (pmu->nr_addr_filters)
device_remove_file(pmu->dev, &dev_attr_nr_addr_filters);
@@ -11863,7 +11864,6 @@ void perf_pmu_unregister(struct pmu *pmu)
put_device(pmu->dev);
}
free_pmu_context(pmu);
- mutex_unlock(&pmus_lock);
}
EXPORT_SYMBOL_GPL(perf_pmu_unregister);
