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authorJames Bottomley <JBottomley@Parallels.com>2014-01-21 07:01:41 -0800
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-05-30 21:52:11 -0700
commite623c2cdb5b9151e1ca8c846e2814977ba4dfcac (patch)
tree51d1d4484bb87179982bd44d872359b60d49dc8e /drivers/scsi
parentc3c8d397fef461c0b3a273f68abf9adffc85aa3a (diff)
downloadlinux-linaro-stable-e623c2cdb5b9151e1ca8c846e2814977ba4dfcac.tar.gz
SCSI: dual scan thread bug fix
commit f2495e228fce9f9cec84367547813cbb0d6db15a upstream. In the highly unusual case where two threads are running concurrently through the scanning code scanning the same target, we run into the situation where one may allocate the target while the other is still using it. In this case, because the reap checks for STARGET_CREATED and kills the target without reference counting, the second thread will do the wrong thing on reap. Fix this by reference counting even creates and doing the STARGET_CREATED check in the final put. Tested-by: Sarah Sharp <sarah.a.sharp@linux.intel.com> Signed-off-by: James Bottomley <JBottomley@Parallels.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/scsi')
-rw-r--r--drivers/scsi/scsi_scan.c23
1 files changed, 16 insertions, 7 deletions
diff --git a/drivers/scsi/scsi_scan.c b/drivers/scsi/scsi_scan.c
index 342876ce53c1..859240408f9e 100644
--- a/drivers/scsi/scsi_scan.c
+++ b/drivers/scsi/scsi_scan.c
@@ -320,6 +320,7 @@ static void scsi_target_destroy(struct scsi_target *starget)
struct Scsi_Host *shost = dev_to_shost(dev->parent);
unsigned long flags;
+ starget->state = STARGET_DEL;
transport_destroy_device(dev);
spin_lock_irqsave(shost->host_lock, flags);
if (shost->hostt->target_destroy)
@@ -384,9 +385,15 @@ static void scsi_target_reap_ref_release(struct kref *kref)
struct scsi_target *starget
= container_of(kref, struct scsi_target, reap_ref);
- transport_remove_device(&starget->dev);
- device_del(&starget->dev);
- starget->state = STARGET_DEL;
+ /*
+ * if we get here and the target is still in the CREATED state that
+ * means it was allocated but never made visible (because a scan
+ * turned up no LUNs), so don't call device_del() on it.
+ */
+ if (starget->state != STARGET_CREATED) {
+ transport_remove_device(&starget->dev);
+ device_del(&starget->dev);
+ }
scsi_target_destroy(starget);
}
@@ -506,11 +513,13 @@ static struct scsi_target *scsi_alloc_target(struct device *parent,
*/
void scsi_target_reap(struct scsi_target *starget)
{
+ /*
+ * serious problem if this triggers: STARGET_DEL is only set in the if
+ * the reap_ref drops to zero, so we're trying to do another final put
+ * on an already released kref
+ */
BUG_ON(starget->state == STARGET_DEL);
- if (starget->state == STARGET_CREATED)
- scsi_target_destroy(starget);
- else
- scsi_target_reap_ref_put(starget);
+ scsi_target_reap_ref_put(starget);
}
/**