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author | Martin Peschke <mpeschke@linux.vnet.ibm.com> | 2013-08-22 17:45:36 +0200 |
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committer | James Bottomley <JBottomley@Parallels.com> | 2013-08-22 08:53:30 -0700 |
commit | d79ff142624e1be080ad8d09101f7004d79c36e1 (patch) | |
tree | 490bd19345fa2dfee17cae0d9fe580e08d6c5d74 | |
parent | 35dc248383bbab0a7203fca4d722875bc81ef091 (diff) | |
download | kernel_goldelico_gta04-d79ff142624e1be080ad8d09101f7004d79c36e1.zip kernel_goldelico_gta04-d79ff142624e1be080ad8d09101f7004d79c36e1.tar.gz kernel_goldelico_gta04-d79ff142624e1be080ad8d09101f7004d79c36e1.tar.bz2 |
[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 c2af7545aaff3495d9bf9a7608c52f0af86fb194
"[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>
-rw-r--r-- | drivers/s390/scsi/zfcp_qdio.c | 8 | ||||
-rw-r--r-- | include/linux/wait.h | 57 |
2 files changed, 59 insertions, 6 deletions
diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c index 665e3cf..de0598e 100644 --- a/drivers/s390/scsi/zfcp_qdio.c +++ b/drivers/s390/scsi/zfcp_qdio.c @@ -224,11 +224,9 @@ int zfcp_qdio_sbals_from_sg(struct zfcp_qdio *qdio, struct zfcp_qdio_req *q_req, static int zfcp_qdio_sbal_check(struct zfcp_qdio *qdio) { - spin_lock_irq(&qdio->req_q_lock); if (atomic_read(&qdio->req_q_free) || !(atomic_read(&qdio->adapter->status) & ZFCP_STATUS_ADAPTER_QDIOUP)) return 1; - spin_unlock_irq(&qdio->req_q_lock); return 0; } @@ -246,9 +244,8 @@ int zfcp_qdio_sbal_get(struct zfcp_qdio *qdio) { long ret; - spin_unlock_irq(&qdio->req_q_lock); - ret = wait_event_interruptible_timeout(qdio->req_q_wq, - zfcp_qdio_sbal_check(qdio), 5 * HZ); + ret = wait_event_interruptible_lock_irq_timeout(qdio->req_q_wq, + zfcp_qdio_sbal_check(qdio), qdio->req_q_lock, 5 * HZ); if (!(atomic_read(&qdio->adapter->status) & ZFCP_STATUS_ADAPTER_QDIOUP)) return -EIO; @@ -262,7 +259,6 @@ int zfcp_qdio_sbal_get(struct zfcp_qdio *qdio) zfcp_erp_adapter_reopen(qdio->adapter, 0, "qdsbg_1"); } - spin_lock_irq(&qdio->req_q_lock); return -EIO; } diff --git a/include/linux/wait.h b/include/linux/wait.h index f487a47..a67fc16 100644 --- a/include/linux/wait.h +++ b/include/linux/wait.h @@ -811,6 +811,63 @@ do { \ __ret; \ }) +#define __wait_event_interruptible_lock_irq_timeout(wq, condition, \ + lock, ret) \ +do { \ + DEFINE_WAIT(__wait); \ + \ + for (;;) { \ + prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE); \ + if (condition) \ + break; \ + if (signal_pending(current)) { \ + ret = -ERESTARTSYS; \ + break; \ + } \ + spin_unlock_irq(&lock); \ + ret = schedule_timeout(ret); \ + spin_lock_irq(&lock); \ + if (!ret) \ + break; \ + } \ + finish_wait(&wq, &__wait); \ +} while (0) + +/** + * wait_event_interruptible_lock_irq_timeout - sleep until a condition gets true or a timeout elapses. + * The condition is checked under the lock. This is expected + * to be called with the lock taken. + * @wq: the waitqueue to wait on + * @condition: a C expression for the event to wait for + * @lock: a locked spinlock_t, which will be released before schedule() + * and reacquired afterwards. + * @timeout: timeout, in jiffies + * + * The process is put to sleep (TASK_INTERRUPTIBLE) until the + * @condition evaluates to true or signal is received. The @condition is + * checked each time the waitqueue @wq is woken up. + * + * wake_up() has to be called after changing any variable that could + * change the result of the wait condition. + * + * This is supposed to be called while holding the lock. The lock is + * dropped before going to sleep and is reacquired afterwards. + * + * The function returns 0 if the @timeout elapsed, -ERESTARTSYS if it + * was interrupted by a signal, and the remaining jiffies otherwise + * if the condition evaluated to true before the timeout elapsed. + */ +#define wait_event_interruptible_lock_irq_timeout(wq, condition, lock, \ + timeout) \ +({ \ + int __ret = timeout; \ + \ + if (!(condition)) \ + __wait_event_interruptible_lock_irq_timeout( \ + wq, condition, lock, __ret); \ + __ret; \ +}) + /* * These are the old interfaces to sleep waiting for an event. |