Re: [PATCH] scsi: libsas: Grab the host lock in sas_ata_device_link_abort()

[Jason Yan]

On 2022/12/21 11:59, Damien Le Moal wrote:
> On 2022/12/21 11:42, Jason Yan wrote:
> > On 2022/12/21 8:36, Damien Le Moal wrote:
> > > On 2022/12/20 23:59, John Garry wrote:
> > > > On 20/12/2022 12:53, Xingui Yang wrote:
> > > > > Grab the host lock in sas_ata_device_link_abort() before calling
> > > >
> > > > This is should be the ata port lock, right? I know that the ata comments
> > > > say differently.
> > > >
> > > > > ata_link_abort(), as the comment in ata_link_abort() mentions.
> > > >
> > > > Can you please add a fixes tag?
> > > >
> > > > > Signed-off-by: Xingui Yang <yangxingui@xxxxxxxxxx>
> > > >
> > > > Reviewed-by: John Garry <john.g.garry@xxxxxxxxxx>
> > > >
> > > > > ---
> > > > >     drivers/scsi/libsas/sas_ata.c | 3 +++
> > > > >     1 file changed, 3 insertions(+)
> > > > >
> > > > > diff --git a/drivers/scsi/libsas/sas_ata.c b/drivers/scsi/libsas/sas_ata.c
> > > > > index f7439bf9cdc6..4f2017b21e6d 100644
> > > > > --- a/drivers/scsi/libsas/sas_ata.c
> > > > > +++ b/drivers/scsi/libsas/sas_ata.c
> > > > > @@ -889,7 +889,9 @@ void sas_ata_device_link_abort(struct domain_device *device, bool force_reset)
> > > > >     {
> > > > >     	struct ata_port *ap = device->sata_dev.ap;
> > > > >     	struct ata_link *link = &ap->link;
> > > > > +	unsigned long flags;
> > > > >     
> > > > > +	spin_lock_irqsave(ap->lock, flags);
> > > > >     	device->sata_dev.fis[2] = ATA_ERR | ATA_DRDY; /* tf status */
> > > > >     	device->sata_dev.fis[3] = ATA_ABORTED; /* tf error */
> > > > >     
> > > > > @@ -897,6 +899,7 @@ void sas_ata_device_link_abort(struct domain_device *device, bool force_reset)
> > > > >     	if (force_reset)
> > > > >     		link->eh_info.action |= ATA_EH_RESET;
> > > > >     	ata_link_abort(link);
> > >
> > > Really need to add lockdep annotations in libata to avoid/catch such bugs...
> > > Will work on that.
> >
> > Actually in libata there are many places calling ata_link_abort() not
> > holding port lock. And some places are holding the real host
> > lock(ata_host->lock) while calling ata_link_abort(). So if you add the
> > lockdep annotations, there may be too many warnings. If these are real
> > issues, we should fix them first.
>
> libata-EH does most of its work without the port lock held because by the time
> we get EH started, we are guaranteed to be idle with no commands in flight. That
> is why the calls you mention look like "bugs" but are not.

What about the interrupt handler such as ahci_error_intr()? I didn't see 
the callers hold the port lock too. Do they need the port lock?