linux-kernel - Re: [PATCH v4 1/5] scsi: ufs: atomic update for clkgating

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Message-ID: <20201027033311.GA1745317@google.com>
Date:   Mon, 26 Oct 2020 20:33:11 -0700
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Can Guo <cang@...eaurora.org>
Cc:     linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, alim.akhtar@...sung.com,
        avri.altman@....com, bvanassche@....org
Subject: Re: [PATCH v4 1/5] scsi: ufs: atomic update for clkgating_enable

On 10/27, Can Guo wrote:
> On 2020-10-27 03:51, Jaegeuk Kim wrote:
> > From: Jaegeuk Kim <jaegeuk@...gle.com>
> > 
> > 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.

> 
> Thanks,
> 
> Can Guo.
> 
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@...gle.com>
> > ---
> >  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;
> >  }