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drbd: Break a deadlock while concurrent fencing and establishing a connection 

When we need to outdate the peer while being promoted to primary,
and the connection gets established at the same time, we deadlock
in drbd_try_outdate_peer() when trying to clear the susp_fen
bit.

Fix this by setting the STATE_SENT bit while holding the mutex.

Using drbd_change_state(.. , CS_HARD, ..) which does not block
until STATE_SENT is cleared, is only for clearness. It does
not contribute anything to the fix.

Signed-off-by: Philipp Reisner <philipp.reisner@linbit.com>
Signed-off-by: Lars Ellenberg <lars.ellenberg@linbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
hifive-unleashed-5.1
Philipp Reisner 2014-04-28 18:43:12 +02:00 committed by Jens Axboe
parent d1e714db81
commit 31007745a5
1 changed files with 13 additions and 10 deletions
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23
drivers/block/drbd/drbd_receiver.c
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@ -1026,24 +1026,27 @@ randomize:
if (drbd_send_protocol(connection) == -EOPNOTSUPP)
return -1;
/* Prevent a race between resync-handshake and
* being promoted to Primary.
*
* Grab and release the state mutex, so we know that any current
* drbd_set_role() is finished, and any incoming drbd_set_role
* will see the STATE_SENT flag, and wait for it to be cleared.
*/
idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
mutex_lock(peer_device->device->state_mutex);
set_bit(STATE_SENT, &connection->flags);
idr_for_each_entry(&connection->peer_devices, peer_device, vnr)
mutex_unlock(peer_device->device->state_mutex);
rcu_read_lock();
idr_for_each_entry(&connection->peer_devices, peer_device, vnr) {
struct drbd_device *device = peer_device->device;
kref_get(&device->kref);
rcu_read_unlock();
/* Prevent a race between resync-handshake and
* being promoted to Primary.
*
* Grab and release the state mutex, so we know that any current
* drbd_set_role() is finished, and any incoming drbd_set_role
* will see the STATE_SENT flag, and wait for it to be cleared.
*/
mutex_lock(device->state_mutex);
mutex_unlock(device->state_mutex);
if (discard_my_data)
set_bit(DISCARD_MY_DATA, &device->flags);
else