On Mon, 2012-08-27 at 12:13 -0400, John Drescher wrote:
> >> I have bisected it down to the following patch:
> >>
> >> Bisecting: 0 revisions left to test after this (roughly 0 steps)
> >> [10f8d5b86743b33d841a175303e2bf67fd620f42] SCSI: fix hot unplug vs
> >> async scan race
> >>
> >> It appears this patch caused the bad behavior although I have not
> >> tested that yet. I am rebuilding the array (takes ~2 hours) from the
> >> previous good bisect.
> >>
>
> Confirmed. This patch appears to cause the bug in my test setup.
>
> [ 339.406778] BUG: soft lockup - CPU#2 stuck for 23s! [kworker/u:8:2202]
[..]
> [ 339.415268] [<ffffffff8141782a>] scsi_remove_target+0xda/0x1f0
I wonder if we are preventing scsi_device_dev_release_usercontext() from
making forward progress?
...the attached patch should confirm this or give more info otherwise.
--
Dan
scsi_remove_target: debug softlockup
From: Dan Williams <d...@fb.com>
dump more info in the case where we get stuck trying to remove a device.
---
drivers/scsi/scsi_sysfs.c | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
index 093d4f6..011f8ee 100644
--- a/drivers/scsi/scsi_sysfs.c
+++ b/drivers/scsi/scsi_sysfs.c
@@ -1032,8 +1032,11 @@ void scsi_remove_target(struct device *dev)
{
struct Scsi_Host *shost = dev_to_shost(dev->parent);
struct scsi_target *starget, *found;
+ struct scsi_target *found_log[3];
unsigned long flags;
+ memset(found_log, 0, sizeof(found_log));
+
restart:
found = NULL;
spin_lock_irqsave(shost->host_lock, flags);
@@ -1041,8 +1044,24 @@ void scsi_remove_target(struct device *dev)
if (starget->state == STARGET_DEL)
continue;
if (starget->dev.parent == dev || &starget->dev == dev) {
+ int i;
+
found = starget;
found->reap_ref++;
+ for (i = 0; i < ARRAY_SIZE(found_log); i++)
+ if (!found_log[i]) {
+ found_log[i] = found;
+ break;
+ } else if (found_log[i] == found) {
+ struct scsi_device *sdev = NULL;
+
+ if (!list_empty(&found->devices))
+ sdev = list_entry(found->devices.next, typeof(*sdev), same_target_siblings);
+ pr_err_once("%s[%d]: reap %d:%d state: %d reap: %d dev_del: %d\n",
+ __func__, i, found->channel, found->id,
+ found->state, found->reap_ref,
+ sdev ? work_busy(&sdev->ew.work) ? 2 : 1 : 0);
+ }
break;
}
}
