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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