closures: fix a race on wakeup from closure_sync

The race was when a thread using closure_sync() notices cl->s->done == 1
before the thread calling closure_put() calls wake_up_process(). Then,
it's possible for that thread to return and exit just before
wake_up_process() is called - so we're trying to wake up a process that
no longer exists.

rcu_read_lock() is sufficient to protect against this, as there's an rcu
barrier somewhere in the process teardown path.

Signed-off-by: Kent Overstreet <[email protected]>
Acked-by: Coly Li <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

0 files changed, 0 insertions, 0 deletions