[PATCH 12/12] closures: fix a race on wakeup from closure_sync

Kent Overstreet
2019-06-10T19:14:54Z

Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
---
lib/closure.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/closure.c b/lib/closure.c
index 46cfe4c382..3e6366c262 100644
--- a/lib/closure.c
+++ b/lib/closure.c
@@ -104,8 +104,14 @@ struct closure_syncer {

static void closure_sync_fn(struct closure *cl)
{
- cl->s->done = 1;
- wake_up_process(cl->s->task);
+ struct closure_syncer *s = cl->s;
+ struct task_struct *p;
+
+ rcu_read_lock();
+ p = READ_ONCE(s->task);
+ s->done = 1;
+ wake_up_process(p);
+ rcu_read_unlock();
}

void __sched __closure_sync(struct closure *cl)
--
2.20.1