From: Philipp Reisner Date: Wed, 23 Jun 2010 09:20:05 +0000 (+0200) Subject: drbd: Fixed a deadlock, probably only affected UP machines X-Git-Tag: firefly_0821_release~7613^2~3690^2~59 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=84dfb9f564208a0331131d1ab922382c7d61a553;p=firefly-linux-kernel-4.4.55.git 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 Signed-off-by: Lars Ellenberg --- diff --git a/drivers/block/drbd/drbd_int.h b/drivers/block/drbd/drbd_int.h index e0e08f5e0a76..aa9bb213fe70 100644 --- a/drivers/block/drbd/drbd_int.h +++ b/drivers/block/drbd/drbd_int.h @@ -947,6 +947,7 @@ struct drbd_conf { union drbd_state state; wait_queue_head_t misc_wait; wait_queue_head_t state_wait; /* upon each state change. */ + wait_queue_head_t net_cnt_wait; unsigned int send_cnt; unsigned int recv_cnt; unsigned int read_cnt; @@ -2018,7 +2019,7 @@ static inline void inc_unacked(struct drbd_conf *mdev) static inline void put_net_conf(struct drbd_conf *mdev) { if (atomic_dec_and_test(&mdev->net_cnt)) - wake_up(&mdev->misc_wait); + wake_up(&mdev->net_cnt_wait); } /** diff --git a/drivers/block/drbd/drbd_main.c b/drivers/block/drbd/drbd_main.c index 440b1d5dcfe2..9fe9bdd9e33d 100644 --- a/drivers/block/drbd/drbd_main.c +++ b/drivers/block/drbd/drbd_main.c @@ -2763,6 +2763,7 @@ void drbd_init_set_defaults(struct drbd_conf *mdev) init_waitqueue_head(&mdev->misc_wait); init_waitqueue_head(&mdev->state_wait); + init_waitqueue_head(&mdev->net_cnt_wait); init_waitqueue_head(&mdev->ee_wait); init_waitqueue_head(&mdev->al_wait); init_waitqueue_head(&mdev->seq_wait); 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 */