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Fix a race between PMU registration and event creation,

Browse source 
and fix pmus_lock vs. pmus_srcu lock ordering.
 
 Signed-off-by: Ingo Molnar <mingo@kernel.org>
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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
This commit is contained in:
Linus Torvalds 2025-03-07 10:38:33 -10:00
commit ab60bd5731
1 changed files with 28 additions and 4 deletions
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32
kernel/events/core.c
View file

@ -11830,6 +11830,21 @@ free_dev:
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);