Commit ab60bd57 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'perf-urgent-2025-03-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 

Pull perf event fixes from Ingo Molnar:
 "Fix a race between PMU registration and event creation, and fix
  pmus_lock vs. pmus_srcu lock ordering"

* tag 'perf-urgent-2025-03-07' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  perf/core: Fix perf_pmu_register() vs. perf_init_event()
  perf/core: Fix pmus_lock vs. pmus_srcu ordering
parents 042751d3 003659fe

kernel/events/core.c

+28 −4
Original line number Diff line number Diff line
@@ -11830,6 +11830,21 @@ static int pmu_dev_alloc(struct pmu *pmu) 
static struct lock_class_key cpuctx_mutex;

static struct lock_class_key cpuctx_lock;



static bool idr_cmpxchg(struct idr *idr, unsigned long id, void *old, void *new)

{

	void *tmp, *val = idr_find(idr, id);



	if (val != old)

		return false;



	tmp = idr_replace(idr, new, id);

	if (IS_ERR(tmp))

		return false;



	WARN_ON_ONCE(tmp != val);

	return true;

}



int perf_pmu_register(struct pmu *pmu, const char *name, int type)

{

	int cpu, ret, max = PERF_TYPE_MAX;
@@ -11856,7 +11871,7 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) 
	if (type >= 0)

		max = type;



	ret = idr_alloc(&pmu_idr, pmu, max, 0, GFP_KERNEL);

	ret = idr_alloc(&pmu_idr, NULL, max, 0, GFP_KERNEL);

	if (ret < 0)

		goto free_pdc;
@@ -11864,6 +11879,7 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) 


	type = ret;

	pmu->type = type;

	atomic_set(&pmu->exclusive_cnt, 0);



	if (pmu_bus_running && !pmu->dev) {

		ret = pmu_dev_alloc(pmu);
@@ -11912,14 +11928,22 @@ int perf_pmu_register(struct pmu *pmu, const char *name, int type) 
	if (!pmu->event_idx)

		pmu->event_idx = perf_event_idx_default;



	/*

	 * Now that the PMU is complete, make it visible to perf_try_init_event().

	 */

	if (!idr_cmpxchg(&pmu_idr, pmu->type, NULL, pmu))

		goto free_context;

	list_add_rcu(&pmu->entry, &pmus);

	atomic_set(&pmu->exclusive_cnt, 0);



	ret = 0;

unlock:

	mutex_unlock(&pmus_lock);



	return ret;



free_context:

	free_percpu(pmu->cpu_pmu_context);



free_dev:

	if (pmu->dev && pmu->dev != PMU_NULL_DEV) {

		device_del(pmu->dev);
@@ -11939,6 +11963,8 @@ 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 +11974,6 @@ 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 +11981,6 @@ 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);