Re: [PATCH 14/15] scsi: libsas: Keep sas host active until finished some work

["chenxiang (M)" <chenxiang66@xxxxxxxxxxxxx>]

在 2021/12/14 20:34, John Garry 写道:
> Please consider som rewrite:
>
> On 17/11/2021 02:45, chenxiang wrote:
>
> "scsi: libsas: Keep sas host active until finished some work" -> 
> "scsi: libsas: Keep host active while processing events"
>
> > From: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
> >
> > For those works from event queue, if executing them such as
> > PORTE_BROADCAST_RCVD when sas host is suspended, it will resume sas host
> > firstly as SMP IOs are sent in the process. So phyup will occur and it
> > will call work PORTE_BYTES_DMAED. But the original work (such as
> > PORTE_BROADCAST_RCVD) and the work PORTE_BYTES_DMAED are in the same
> > singlethread workqueue, so the complete of original work waits for
> > the complete of work PORTE_BYTES_DMAED while the complete of work
> > PORTE_BYTES_DMAED wait for the complete of original and it is blocked.
> >
> > So call pm_runtime_get_noresume() to keep sas host active until
> > finished those works.
> Processing events such as PORTE_BROADCAST_RCVD may cause dependency 
> issues for runtime power management support.
>
> Such a problem would be that handling a PORTE_BROADCAST_RCVD event 
> requires that the host is resumed to send SMP commands. However, in 
> resuming the host, the phyup events generated from re-enabling the 
> phys are processed in the same workqueue as the original 
> PORTE_BROADCAST_RCVD event. As such, the host will never finish 
> resuming (as it waits for the phyup event processing), and then the 
> PORTE_BROADCAST_RCVD event cannot be processed as the SMP commands are 
> blocked, and so we have a deadlock.
>
> Solve this problem by ensuring that libsas keeps the host active until 
> completely finished processing phy or port events, such as 
> PORTE_BYTES_DMAED. As such, we don't have to worry about resuming the 
> host for processing individual SMP commands in this example.

ok, i will consider to rewrite them.

> > Signed-off-by: Xiang Chen <chenxiang66@xxxxxxxxxxxxx>
> > Reviewed-by: John Garry <john.garry@xxxxxxxxxx>
> > ---
> >   drivers/scsi/libsas/sas_event.c | 24 +++++++++++++++++++++---
> >   1 file changed, 21 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/scsi/libsas/sas_event.c 
> > b/drivers/scsi/libsas/sas_event.c
> > index 626ef96b9348..3613b9b315bc 100644
> > --- a/drivers/scsi/libsas/sas_event.c
> > +++ b/drivers/scsi/libsas/sas_event.c
> > @@ -50,8 +50,10 @@ void sas_queue_deferred_work(struct sas_ha_struct 
> > *ha)
> >       list_for_each_entry_safe(sw, _sw, &ha->defer_q, drain_node) {
> >           list_del_init(&sw->drain_node);
> >           ret = sas_queue_work(ha, sw);
> > -        if (ret != 1)
> > +        if (ret != 1) {
> > +            pm_runtime_put(ha->dev);
> > sas_free_event(to_asd_sas_event(&sw->work));
> > +        }
> >       }
> >       spin_unlock_irq(&ha->lock);
> >   }
> > @@ -126,16 +128,22 @@ void sas_enable_revalidation(struct 
> > sas_ha_struct *ha)
> >   static void sas_port_event_worker(struct work_struct *work)
> >   {
> >       struct asd_sas_event *ev = to_asd_sas_event(work);
> > +    struct asd_sas_phy *phy = ev->phy;
> > +    struct sas_ha_struct *ha = phy->ha;
> >         sas_port_event_fns[ev->event](work);
> > +    pm_runtime_put(ha->dev);
> >       sas_free_event(ev);
> >   }
> >     static void sas_phy_event_worker(struct work_struct *work)
> >   {
> >       struct asd_sas_event *ev = to_asd_sas_event(work);
> > +    struct asd_sas_phy *phy = ev->phy;
> > +    struct sas_ha_struct *ha = phy->ha;
> >         sas_phy_event_fns[ev->event](work);
> > +    pm_runtime_put(ha->dev);
> >       sas_free_event(ev);
> >   }
> >   @@ -170,14 +178,19 @@ int sas_notify_port_event(struct asd_sas_phy 
> > *phy, enum port_event event,
> >       if (!ev)
> >           return -ENOMEM;
> >   +    /* Call pm_runtime_put() with pairs in sas_port_event_worker() */
> > +    pm_runtime_get_noresume(ha->dev);
> > +
> >       INIT_SAS_EVENT(ev, sas_port_event_worker, phy, event);
> >         if (sas_defer_event(phy, ev))
> >           return 0;
> >         ret = sas_queue_event(event, &ev->work, ha);
> > -    if (ret != 1)
> > +    if (ret != 1) {
> > +        pm_runtime_put(ha->dev);
> >           sas_free_event(ev);
> > +    }
> >         return ret;
> >   }
> > @@ -196,14 +209,19 @@ int sas_notify_phy_event(struct asd_sas_phy 
> > *phy, enum phy_event event,
> >       if (!ev)
> >           return -ENOMEM;
> >   +    /* Call pm_runtime_put() with pairs in sas_phy_event_worker() */
> > +    pm_runtime_get_noresume(ha->dev);
> > +
> >       INIT_SAS_EVENT(ev, sas_phy_event_worker, phy, event);
> >         if (sas_defer_event(phy, ev))
> >           return 0;
> >         ret = sas_queue_event(event, &ev->work, ha);
> > -    if (ret != 1)
> > +    if (ret != 1) {
> > +        pm_runtime_put(ha->dev);
> >           sas_free_event(ev);
> > +    }
> >         return ret;
> >   }
>
>
> .