Commit 2565e425 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

perf/core: Fix pmus_lock vs. pmus_srcu ordering 



Commit a63fbed7 ("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: a63fbed7 ("perf/tracing/cpuhotplug: Fix locking order")
Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarIngo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20241104135517.679556858@infradead.org
parent df87d843

kernel/events/core.c

+2 −2
Original line number Diff line number Diff line
@@ -11939,6 +11939,8 @@ 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
@@ -11948,7 +11950,6 @@ 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);
@@ -11956,7 +11957,6 @@ 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);