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authorMartin Peschke <mpeschke@linux.vnet.ibm.com>2013-08-22 17:45:36 +0200
committerJames Bottomley <JBottomley@Parallels.com>2013-08-22 08:53:30 -0700
commitd79ff142624e1be080ad8d09101f7004d79c36e1 (patch)
tree490bd19345fa2dfee17cae0d9fe580e08d6c5d74 /drivers/s390/scsi
parent35dc248383bbab0a7203fca4d722875bc81ef091 (diff)
downloadlinux-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>
Diffstat (limited to 'drivers/s390/scsi')
-rw-r--r--drivers/s390/scsi/zfcp_qdio.c8
1 files changed, 2 insertions, 6 deletions
diff --git a/drivers/s390/scsi/zfcp_qdio.c b/drivers/s390/scsi/zfcp_qdio.c
index 665e3cfaaf85..de0598eaacd2 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;
}