[SCSI] zfcp: fix lock imbalance by reworking request queue locking
This patch adds wait_event_interruptible_lock_irq_timeout(), which is a
straight-forward descendant of wait_event_interruptible_timeout() and
wait_event_interruptible_lock_irq().
The zfcp driver used to call wait_event_interruptible_timeout()
in combination with some intricate and error-prone locking. Using
wait_event_interruptible_lock_irq_timeout() as a replacement
nicely cleans up that locking.
This rework removes a situation that resulted in a locking imbalance
in zfcp_qdio_sbal_get():
BUG: workqueue leaked lock or atomic: events/1/0xffffff00/10
last function: zfcp_fc_wka_port_offline+0x0/0xa0 [zfcp]
It was introduced by commit c2af7545aa
"[SCSI] zfcp: Do not wait for SBALs on stopped queue", which had a new
code path related to ZFCP_STATUS_ADAPTER_QDIOUP that took an early exit
without a required lock being held. The problem occured when a
special, non-SCSI I/O request was being submitted in process context,
when the adapter's queues had been torn down. In this case the bug
surfaced when the Fibre Channel port connection for a well-known address
was closed during a concurrent adapter shut-down procedure, which is a
rare constellation.
This patch also fixes these warnings from the sparse tool (make C=1):
drivers/s390/scsi/zfcp_qdio.c:224:12: warning: context imbalance in
'zfcp_qdio_sbal_check' - wrong count at exit
drivers/s390/scsi/zfcp_qdio.c:244:5: warning: context imbalance in
'zfcp_qdio_sbal_get' - unexpected unlock
Last but not least, we get rid of that crappy lock-unlock-lock
sequence at the beginning of the critical section.
It is okay to call zfcp_erp_adapter_reopen() with req_q_lock held.
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Reported-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Peschke <mpeschke@linux.vnet.ibm.com>
Cc: stable@vger.kernel.org #2.6.35+
Signed-off-by: Steffen Maier <maier@linux.vnet.ibm.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Родитель
35dc248383
Коммит
d79ff14262
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@ -224,11 +224,9 @@ int zfcp_qdio_sbals_from_sg(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req,
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static int zfcp_qdio_sbal_check(struct zfcp_qdio *qdio)
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{
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spin_lock_irq(&qdio->req_q_lock);
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if (atomic_read(&qdio->req_q_free) ||
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!(atomic_read(&qdio->adapter->status) & ZFCP_STATUS_ADAPTER_QDIOUP))
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return 1;
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spin_unlock_irq(&qdio->req_q_lock);
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return 0;
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}
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@ -246,9 +244,8 @@ int zfcp_qdio_sbal_get(struct zfcp_qdio *qdio)
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{
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long ret;
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spin_unlock_irq(&qdio->req_q_lock);
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ret = wait_event_interruptible_timeout(qdio->req_q_wq,
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zfcp_qdio_sbal_check(qdio), 5 * HZ);
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ret = wait_event_interruptible_lock_irq_timeout(qdio->req_q_wq,
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zfcp_qdio_sbal_check(qdio), qdio->req_q_lock, 5 * HZ);
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if (!(atomic_read(&qdio->adapter->status) & ZFCP_STATUS_ADAPTER_QDIOUP))
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return -EIO;
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@ -262,7 +259,6 @@ int zfcp_qdio_sbal_get(struct zfcp_qdio *qdio)
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zfcp_erp_adapter_reopen(qdio->adapter, 0, "qdsbg_1");
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}
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spin_lock_irq(&qdio->req_q_lock);
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return -EIO;
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}
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@ -811,6 +811,63 @@ do { \
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__ret; \
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})
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#define __wait_event_interruptible_lock_irq_timeout(wq, condition, \
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lock, ret) \
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do { \
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DEFINE_WAIT(__wait); \
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\
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for (;;) { \
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prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE); \
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if (condition) \
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break; \
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if (signal_pending(current)) { \
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ret = -ERESTARTSYS; \
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break; \
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} \
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spin_unlock_irq(&lock); \
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ret = schedule_timeout(ret); \
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spin_lock_irq(&lock); \
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if (!ret) \
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break; \
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} \
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finish_wait(&wq, &__wait); \
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} while (0)
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/**
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* wait_event_interruptible_lock_irq_timeout - sleep until a condition gets true or a timeout elapses.
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* The condition is checked under the lock. This is expected
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* to be called with the lock taken.
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* @wq: the waitqueue to wait on
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* @condition: a C expression for the event to wait for
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* @lock: a locked spinlock_t, which will be released before schedule()
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* and reacquired afterwards.
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* @timeout: timeout, in jiffies
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*
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* The process is put to sleep (TASK_INTERRUPTIBLE) until the
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* @condition evaluates to true or signal is received. The @condition is
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* checked each time the waitqueue @wq is woken up.
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*
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* wake_up() has to be called after changing any variable that could
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* change the result of the wait condition.
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*
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* This is supposed to be called while holding the lock. The lock is
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* dropped before going to sleep and is reacquired afterwards.
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*
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* The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it
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* was interrupted by a signal, and the remaining jiffies otherwise
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* if the condition evaluated to true before the timeout elapsed.
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*/
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#define wait_event_interruptible_lock_irq_timeout(wq, condition, lock, \
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timeout) \
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({ \
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int __ret = timeout; \
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\
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if (!(condition)) \
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__wait_event_interruptible_lock_irq_timeout( \
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wq, condition, lock, __ret); \
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__ret; \
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})
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/*
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* These are the old interfaces to sleep waiting for an event.
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