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scsi: restart list search after unlock in scsi_remove_target 

When dropping a lock while iterating a list we must restart the search
as other threads could have manipulated the list under us.  Without this
we can get stuck in an endless loop.  This bug was introduced by

commit bc3f02a795
Author: Dan Williams <djbw@fb.com>
Date:   Tue Aug 28 22:12:10 2012 -0700

    [SCSI] scsi_remove_target: fix softlockup regression on hot remove

Which was itself trying to fix a reported soft lockup issue

http://thread.gmane.org/gmane.linux.kernel/1348679

However, we believe even with this revert of the original patch, the soft
lockup problem has been fixed by

commit f2495e228f
Author: James Bottomley <JBottomley@Parallels.com>
Date:   Tue Jan 21 07:01:41 2014 -0800

    [SCSI] dual scan thread bug fix

Thanks go to Dan Williams <dan.j.williams@intel.com> for tracking all this
prior history down.

Reported-by: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Tested-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Johannes Thumshirn <jthumshirn@suse.de>
Fixes: bc3f02a795
Cc: stable@vger.kernel.org
Signed-off-by: James Bottomley <JBottomley@Odin.com>
This commit is contained in:
Christoph Hellwig 2015-10-19 16:35:46 +02:00 committed by James Bottomley
parent a82544c7ba
commit 4099819356
1 changed files with 4 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

16
drivers/scsi/scsi_sysfs.c
View File

@ -1158,31 +1158,23 @@ 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, *last = NULL;
struct scsi_target *starget;
unsigned long flags;
/* remove targets being careful to lookup next entry before
* deleting the last
*/
restart:
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) {
/* assuming new targets arrive at the end */
kref_get(&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);
scsi_target_reap(starget);
goto restart;
}
}
spin_unlock_irqrestore(shost->host_lock, flags);
if (last)
scsi_target_reap(last);
}
EXPORT_SYMBOL(scsi_remove_target);