On Mon, 2015-10-19 at 16:35 +0200, Christoph Hellwig 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.
>
> Reported-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
>
> 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);
Hi Christoph,
I haven't heard anything from the original reporter of the lockup but
my test's went all O.K., so
Tested-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
>
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