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drbd: Fixed a deadlock, probably only affected UP machines

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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>
This commit is contained in:
Philipp Reisner
2010-06-23 11:20:05 +02:00
parent 65d922c33e
commit 84dfb9f564
3 changed files with 4 additions and 2 deletions
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drivers/block/drbd/drbd_int.h
+2 -1
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@@ -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);
}
/**