Hi Dan,
This fix should go into stable tree too, as I know several stable tree
already include commit 3b661a9. Maybe James can add stable cc.
Best regards!
Jack
> John reports:
> BUG: soft lockup - CPU#2 stuck for 23s! [kworker/u:8:2202]
> [..]
> Call Trace:
> [<ffffffff8141782a>] scsi_remove_target+0xda/0x1f0
> [<ffffffff81421de5>] sas_rphy_remove+0x55/0x60
> [<ffffffff81421e01>] sas_rphy_delete+0x11/0x20
> [<ffffffff81421e35>] sas_port_delete+0x25/0x160
> [<ffffffff814549a3>] mptsas_del_end_device+0x183/0x270
>
> ...introduced by commit 3b661a9 "[SCSI] fix hot unplug vs async scan
race".
>
> Don't restart lookup of more stargets in the multi-target case, just
> arrange to traverse the list once, on the assumption that new targets
> are always added at the end. There is no guarantee that the target will
> change state in scsi_target_reap() so we can end up spinning if we
> restart.
>
> LKML-Reference:
> <CAEhu1-6wq1YsNiscGMwP4ud0Q+MrViRzv=kcwcqsbnc8c68...@mail.gmail.com>
> Reported-by: John Drescher <dresche...@gmail.com>
> Tested-by: John Drescher <dresche...@gmail.com>
> Signed-off-by: Dan Williams <d...@fb.com>
> ---
> drivers/scsi/scsi_sysfs.c | 30 ++++++++++++++----------------
> 1 file changed, 14 insertions(+), 16 deletions(-)
>
> diff --git a/drivers/scsi/scsi_sysfs.c b/drivers/scsi/scsi_sysfs.c
> index 093d4f6..ce5224c 100644
> --- a/drivers/scsi/scsi_sysfs.c
> +++ b/drivers/scsi/scsi_sysfs.c
> @@ -1031,33 +1031,31 @@ 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, *found;
> + struct scsi_target *starget, *last = NULL;
> unsigned long flags;
>
> - restart:
> - found = NULL;
> + /* remove targets being careful to lookup next entry before
> + * deleting the last
> + */
> 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) {
> - found = starget;
> - found->reap_ref++;
> - break;
> + /* assuming new targets arrive at the end */
> + 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);
> }
> }
> spin_unlock_irqrestore(shost->host_lock, flags);
>
> - if (found) {
> - __scsi_remove_target(found);
> - scsi_target_reap(found);
> - /* in the case where @dev has multiple starget children,
> - * continue removing.
> - *
> - * FIXME: does such a case exist?
> - */
> - goto restart;
> - }
> + if (last)
> + scsi_target_reap(last);
> }
> EXPORT_SYMBOL(scsi_remove_target);
>
>
> --
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