Re: [PATCH 0/3] SCSI: Fix hard lockup in scsi_remove_target()

From: Johannes Thumshirn
Date: Fri Oct 16 2015 - 07:24:52 EST


On Wed, 2015-10-14 at 11:18 -0700, Christoph Hellwig wrote:
> On Wed, Oct 14, 2015 at 08:45:56AM -0700, James Bottomley wrote:
> > OK, so I really need you to separate the problems. Fixing the bug

[..]

>
> Johannes, can you test the patch below?

I've tested your patch and it doesn't show the lockup anymore, so far
so good. But it seems as if I have a problem in my test setup, because
I can't reproduce the bug on vanilla 4.3-rc5 either. I will ask the
original reporter if it is possible to test your patch on their side.

Appart from that it looks good to me (and much simpler than my changes)
.

>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index b333389f..d3b34d8 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -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);
>
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