From patchwork Fri Oct 19 10:48:57 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [SCSI] scsi_remove_target: fix softlockup regression on hot remove Date: Fri, 19 Oct 2012 00:48:57 -0000 From: Louis Bouchard X-Patchwork-Id: 192662 Message-Id: <1350643737-14836-2-git-send-email-louis.bouchard@canonical.com> To: kernel-team@lists.ubuntu.com From: Dan Williams John reports: BUG: soft lockup - CPU#2 stuck for 23s! [kworker/u:8:2202] [..] Call Trace: [] scsi_remove_target+0xda/0x1f0 [] sas_rphy_remove+0x55/0x60 [] sas_rphy_delete+0x11/0x20 [] sas_port_delete+0x25/0x160 [] 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: Acked-by: Jack Wang LKML-Reference: Reported-by: John Drescher Tested-by: John Drescher Signed-off-by: Dan Williams Signed-off-by: James Bottomley (cherry picked from commit bc3f02a795d3b4faa99d37390174be2a75d091bd) BugLink: http://bugs.launchpad.net/bugs/1056746 Signed-off-by: Louis Bouchard Acked-by: Andy Whitcroft --- drivers/scsi/scsi_sysfs.c | 30 ++++++++++++++---------------- 1 file changed, 14 insertions(+), 16 deletions(-) diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c index bb7c482..08d48a3 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);