[tip:perf/core] perf: Sanitize the RCU logic

tip-bot for Peter Zijlstra
2010-09-13T15:19:16Z

Commit-ID: cde8e88498c8de69271fcb6d4dd974979368fa67
Gitweb: http://git.kernel.org/tip/cde8e88498c8de69271fcb6d4dd974979368fa67
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
AuthorDate: Mon, 13 Sep 2010 11:06:55 +0200
Committer: Ingo Molnar <mingo@elte.hu>
CommitDate: Mon, 13 Sep 2010 17:08:42 +0200

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>
---
kernel/perf_event.c | 17 +++++++++--------
1 files changed, 9 insertions(+), 8 deletions(-)

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 @@ static void perf_event_task_event(struct perf_task_event *task_event)
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 @@ static void perf_event_task_event(struct perf_task_event *task_event)
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 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)

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 @@ static void perf_event_comm_event(struct perf_comm_event *comm_event)
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 @@ got_name:

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 @@ got_name:
vma->vm_flags & VM_EXEC);
}
}
- rcu_read_unlock_sched();
+ rcu_read_unlock();

kfree(buf);
}
@@ -5218,10 +5218,11 @@ void perf_pmu_unregister(struct pmu *pmu)
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);