Re: [PATCH v4 1/5] scsi: ufs: atomic update for clkgating_enable

[Can Guo]

On 2020-10-27 11:33, Jaegeuk Kim wrote:
> On 10/27, Can Guo wrote:
> > On 2020-10-27 03:51, Jaegeuk Kim wrote:
> > > From: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > >
> > > When giving a stress test which enables/disables clkgating, we hit
> > > device
> > > timeout sometimes. This patch avoids subtle racy condition to address
> > > it.
> > >
> > > Note that, this requires a patch to address the device stuck by
> > > REQ_CLKS_OFF in
> > > __ufshcd_release().
> > >
> > > The fix is "scsi: ufs: avoid to call REQ_CLKS_OFF to CLKS_OFF".
> >
> > Why don't you just squash the fix into this one?
>
> I'm seeing this patch just revealed that problem.

That scenario (back to back calling of ufshcd_release()) only happens
when you stress the clkgate_enable sysfs node, so let's keep the fix
as one to make things simple. What do you think?

Thanks,

Can Guo.

> > Thanks,
> >
> > Can Guo.
> >
> > >
> > > Signed-off-by: Jaegeuk Kim <jaegeuk@xxxxxxxxxx>
> > > ---
> > >  drivers/scsi/ufs/ufshcd.c | 12 ++++++------
> > >  1 file changed, 6 insertions(+), 6 deletions(-)
> > >
> > > diff --git a/drivers/scsi/ufs/ufshcd.c b/drivers/scsi/ufs/ufshcd.c
> > > index cc8d5f0c3fdc..6c9269bffcbd 100644
> > > --- a/drivers/scsi/ufs/ufshcd.c
> > > +++ b/drivers/scsi/ufs/ufshcd.c
> > > @@ -1808,19 +1808,19 @@ static ssize_t
> > > ufshcd_clkgate_enable_store(struct device *dev,
> > >  		return -EINVAL;
> > >
> > >  	value = !!value;
> > > +
> > > +	spin_lock_irqsave(hba->host->host_lock, flags);
> > >  	if (value == hba->clk_gating.is_enabled)
> > >  		goto out;
> > >
> > > -	if (value) {
> > > -		ufshcd_release(hba);
> > > -	} else {
> > > -		spin_lock_irqsave(hba->host->host_lock, flags);
> > > +	if (value)
> > > +		__ufshcd_release(hba);
> > > +	else
> > >  		hba->clk_gating.active_reqs++;
> > > -		spin_unlock_irqrestore(hba->host->host_lock, flags);
> > > -	}
> > >
> > >  	hba->clk_gating.is_enabled = value;
> > >  out:
> > > +	spin_unlock_irqrestore(hba->host->host_lock, flags);
> > >  	return count;
> > >  }