perf: Sanitize the RCU logic
Simplify things and simply synchronize against two RCU variants for
PMU unregister -- we don't care about performance, its module unload
if anything.
Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
diff --git a/kernel/perf_event.c b/kernel/perf_event.c
index f29b525..bc46bff 100644
--- a/kernel/perf_event.c
+++ b/kernel/perf_event.c
@@ -3810,7 +3810,7 @@
struct pmu *pmu;
int ctxn;
- rcu_read_lock_sched();
+ rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
perf_event_task_ctx(&cpuctx->ctx, task_event);
@@ -3825,7 +3825,7 @@
if (ctx)
perf_event_task_ctx(ctx, task_event);
}
- rcu_read_unlock_sched();
+ rcu_read_unlock();
}
static void perf_event_task(struct task_struct *task,
@@ -3943,7 +3943,7 @@
comm_event->event_id.header.size = sizeof(comm_event->event_id) + size;
- rcu_read_lock_sched();
+ rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
perf_event_comm_ctx(&cpuctx->ctx, comm_event);
@@ -3956,7 +3956,7 @@
if (ctx)
perf_event_comm_ctx(ctx, comm_event);
}
- rcu_read_unlock_sched();
+ rcu_read_unlock();
}
void perf_event_comm(struct task_struct *task)
@@ -4126,7 +4126,7 @@
mmap_event->event_id.header.size = sizeof(mmap_event->event_id) + size;
- rcu_read_lock_sched();
+ rcu_read_lock();
list_for_each_entry_rcu(pmu, &pmus, entry) {
cpuctx = this_cpu_ptr(pmu->pmu_cpu_context);
perf_event_mmap_ctx(&cpuctx->ctx, mmap_event,
@@ -4142,7 +4142,7 @@
vma->vm_flags & VM_EXEC);
}
}
- rcu_read_unlock_sched();
+ rcu_read_unlock();
kfree(buf);
}
@@ -5218,10 +5218,11 @@
mutex_unlock(&pmus_lock);
/*
- * We use the pmu list either under SRCU or preempt_disable,
- * synchronize_srcu() implies synchronize_sched() so we're good.
+ * We dereference the pmu list under both SRCU and regular RCU, so
+ * synchronize against both of those.
*/
synchronize_srcu(&pmus_srcu);
+ synchronize_rcu();
free_percpu(pmu->pmu_disable_count);
free_pmu_context(pmu->pmu_cpu_context);