On Wed, 2015-11-04 at 14:35 -0800, Bart Van Assche wrote:
> On 10/30/2015 03:09 PM, Bart Van Assche wrote:
> > When dropping a lock while iterating a list we must restart the search
> > as other threads could have manipulated the list under us. Without this
> > we can get stuck in an endless loop.
> >
> > This is a slightly modified version of a patch from Christoph Hellwig
> > (see also https://www.spinics.net/lists/linux-scsi/msg89416.html).
> >
> > Reported-by: Johannes Thumshirn <jthumsh...@suse.de>
> > Signed-off-by: Bart Van Assche <bart.vanass...@sandisk.com>
> > Cc: Johannes Thumshirn <jthumsh...@suse.de>
> > Cc: Christoph Hellwig <h...@lst.de>
> > Cc: Dan Williams <dan.j.willi...@intel.com>
> > Cc: stable <sta...@vger.kernel.org>
> > ---
> > drivers/scsi/scsi_sysfs.c | 16 ++++------------
> > 1 file changed, 4 insertions(+), 12 deletions(-)
> >
> > diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> > index b9fb61a..5a183d1 100644
> > --- a/drivers/scsi/scsi_sysfs.c
> > +++ b/drivers/scsi/scsi_sysfs.c
> > @@ -1158,32 +1158,24 @@ 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->reaped)
> > continue;
> > if (starget->dev.parent == dev || &starget->dev == dev) {
> > - /* assuming new targets arrive at the end */
> > kref_get(&starget->reap_ref);
> > starget->reaped = true;
> > 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);
>
> (replying to my own e-mail)
>
> Hello Christoph,
>
> Is it OK for you if I mention you as author of this e-mail ?
Could you just both co-operate, especially since there's not much
difference between the patches.
The fundamental problem with this is how have the conditions that caused
us to move away from list restart:
commit bc3f02a795d3b4faa99d37390174be2a75d091bd
Author: Dan Williams <d...@fb.com>
Date: Tue Aug 28 22:12:10 2012 -0700
[SCSI] scsi_remove_target: fix softlockup regression on hot remove
Which was triggered by this bug report
http://thread.gmane.org/gmane.linux.kernel/1348679
been mitigated?
James
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