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s390/zcrypt: fix possible deadlock situation on ap queue remove 

With commit 01396a374c ("s390/zcrypt: revisit ap device remove
procedure") the ap queue remove is now a two stage process. However,
a del_timer_sync() call may trigger the timer function which may
try to lock the very same spinlock as is held by the function
just initiating the del_timer_sync() call. This could end up in
a deadlock situation. Very unlikely but possible as you need to
remove an ap queue at the exact sime time when a timeout of a
request occurs.

Signed-off-by: Harald Freudenberger <freude@linux.ibm.com>
Reported-by: Pierre Morel <pmorel@linux.ibm.com>
Fixes: commit 01396a374c ("s390/zcrypt: revisit ap device remove procedure")
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Harald Freudenberger 2019-04-03 13:18:22 +02:00 committed by Martin Schwidefsky
parent 5712f3301a
commit 16222cfb96
1 changed files with 1 additions and 1 deletions
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2
drivers/s390/crypto/ap_queue.c
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@ -751,8 +751,8 @@ void ap_queue_prepare_remove(struct ap_queue *aq)
__ap_flush_queue(aq);
/* set REMOVE state to prevent new messages are queued in */
aq->state = AP_STATE_REMOVE;
del_timer_sync(&aq->timeout);
spin_unlock_bh(&aq->lock);
del_timer_sync(&aq->timeout);
}
void ap_queue_remove(struct ap_queue *aq)