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authorDan Williams <djbw@fb.com>2012-08-28 22:12:10 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2012-10-07 08:32:29 -0700
commitb8d54c01874da4e548a531b77a29c21236ce8a31 (patch)
treec511ba3df767df0001d28c1bb8a6b92b1b4f3be4
parent4a3bb116ee8ab2f912fdb6d2af40028b15825151 (diff)
downloadlinux-linaro-stable-b8d54c01874da4e548a531b77a29c21236ce8a31.tar.gz
SCSI: scsi_remove_target: fix softlockup regression on hot remove
commit bc3f02a795d3b4faa99d37390174be2a75d091bd upstream. 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. 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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--drivers/scsi/scsi_sysfs.c30
1 files changed, 14 insertions, 16 deletions
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index bb7c4828acc0..08d48a3b7679 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1023,33 +1023,31 @@ 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);