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[SCSI] scsi_remove_target: fix softlockup regression on hot remove 

John reports:
 BUG: soft lockup - CPU#2 stuck for 23s! [kworker/u:8:2202]
 [..]
 Call Trace:
  [<ffffffff8141782a>] scsi_remove_target+0xda/0x1f0
  [<ffffffff81421de5>] sas_rphy_remove+0x55/0x60
  [<ffffffff81421e01>] sas_rphy_delete+0x11/0x20
  [<ffffffff81421e35>] sas_port_delete+0x25/0x160
  [<ffffffff814549a3>] mptsas_del_end_device+0x183/0x270

...introduced by commit 3b661a9 "[SCSI] fix hot unplug vs async scan race".

Don't restart lookup of more stargets in the multi-target case, just
arrange to traverse the list once, on the assumption that new targets
are always added at the end.  There is no guarantee that the target will
change state in scsi_target_reap() so we can end up spinning if we
restart.

Cc: <stable@vger.kernel.org>
Acked-by: Jack Wang <jack_wang@usish.com>
LKML-Reference: <CAEhu1-6wq1YsNiscGMwP4ud0Q+MrViRzv=kcWCQSBNc8c68N5Q@mail.gmail.com>
Reported-by: John Drescher <drescherjm@gmail.com>
Tested-by: John Drescher <drescherjm@gmail.com>
Signed-off-by: Dan Williams <djbw@fb.com>
Signed-off-by: James Bottomley <JBottomley@Parallels.com>
This commit is contained in:
Dan Williams 2012-08-28 22:12:10 -07:00 committed by James Bottomley
parent 225c56960f
commit bc3f02a795
1 changed files with 14 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

30
drivers/scsi/scsi_sysfs.c
View File

@ -1031,33 +1031,31 @@ static void __scsi_remove_target(struct scsi_target *starget)
void scsi_remove_target(struct device *dev)
{
struct Scsi_Host *shost = dev_to_shost(dev->parent);
struct scsi_target *starget, *found;
struct scsi_target *starget, *last = NULL;
unsigned long flags;
restart:
found = NULL;
/* remove targets being careful to lookup next entry before
* deleting the last
*/
spin_lock_irqsave(shost->host_lock, flags);
list_for_each_entry(starget, &shost->__targets, siblings) {
if (starget->state == STARGET_DEL)
continue;
if (starget->dev.parent == dev || &starget->dev == dev) {
found = starget;
found->reap_ref++;
break;
/* assuming new targets arrive at the end */
starget->reap_ref++;
spin_unlock_irqrestore(shost->host_lock, flags);
if (last)
scsi_target_reap(last);
last = starget;
__scsi_remove_target(starget);
spin_lock_irqsave(shost->host_lock, flags);
}
}
spin_unlock_irqrestore(shost->host_lock, flags);
if (found) {
__scsi_remove_target(found);
scsi_target_reap(found);
/* in the case where @dev has multiple starget children,
* continue removing.
*
* FIXME: does such a case exist?
*/
goto restart;
}
if (last)
scsi_target_reap(last);
}
EXPORT_SYMBOL(scsi_remove_target);