drbd: Fixed a deadlock, probably only affected UP machines

After disconnect (most likely mdev->net_cnt == 0) and we are
still in an unstable state (!drbd_state_is_stable()). When we
get an IO request in drbd_get_max_buffers() (called from
__inc_ap_bio_cond(), called from inc_ap_bio()) we wake up
misc_wait. Misc_wait is also used in inc_ap_bio() to sleep
until the outcome of __inc_ap_bio_cond() changes. => Busy loop!

Solution: Have a dedicated wait queue for get_net_conf() and
put_net_conf().

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>

1 files changed, 1 insertions, 1 deletions

diff --git a/drivers/block/drbd/drbd_receiver.c b/drivers/block/drbd/drbd_receiver.c
index 224c79ed16e9..22d74d79ba42 100644
--- a/drivers/block/drbd/drbd_receiver.c
+++ b/drivers/block/drbd/drbd_receiver.c
@@ -3775,7 +3775,7 @@ static void drbd_disconnect(struct drbd_conf *mdev)
 
         if (os.conn == C_DISCONNECTING) {
                 struct hlist_head *h;
-                wait_event(mdev->misc_wait, atomic_read(&mdev->net_cnt) == 0);
+                wait_event(mdev->net_cnt_wait, atomic_read(&mdev->net_cnt) == 0);
 
                 /* we must not free the tl_hash
                  * while application io is still on the fly */