Re: [PATCH v1] scsi: ufs: Fix ufshcd_scale_clks decision in recovery flow

[Bart Van Assche]

On 7/30/22 00:08, Stanley Chu wrote:
> Hi Bart,
>
> On Sat, Jul 30, 2022 at 4:12 AM Bart Van Assche <bvanassche@xxxxxxx> wrote:
> > On 7/29/22 00:55, Stanley Chu wrote:
> > > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> > > index 581d88af07ab..dc57a7988023 100644
> > > --- a/drivers/ufs/core/ufshcd.c
> > > +++ b/drivers/ufs/core/ufshcd.c
> > > @@ -1574,8 +1574,6 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
> > >        ufshcd_rpm_get_sync(hba);
> > >        ufshcd_hold(hba, false);
> > >
> > > -     hba->clk_scaling.is_enabled = value;
> > > -
> > >        if (value) {
> > >                ufshcd_resume_clkscaling(hba);
> > >        } else {
> > > @@ -1586,6 +1584,8 @@ static ssize_t ufshcd_clkscale_enable_store(struct device *dev,
> > >                                        __func__, err);
> > >        }
> > >
> > > +     hba->clk_scaling.is_enabled = value;
> > > +
> > >        ufshcd_release(hba);
> > >        ufshcd_rpm_put_sync(hba);
> > >    out:
> > > @@ -7259,7 +7259,8 @@ static int ufshcd_host_reset_and_restore(struct ufs_hba *hba)
> > >        hba->silence_err_logs = false;
> > >
> > >        /* scale up clocks to max frequency before full reinitialization */
> > > -     ufshcd_scale_clks(hba, true);
> > > +     if (ufshcd_is_clkscaling_supported(hba) && hba->clk_scaling.is_enabled)
> > > +             ufshcd_scale_clks(hba, true);
> > >
> > >        err = ufshcd_hba_enable(hba);
> >
> > I see a race condition between the hba->clk_scaling.is_enabled check in
> > ufshcd_host_reset_and_restore() and the code that sets
> > ufshcd_clkscale_enable_store(). Shouldn't the code in
> > ufshcd_host_reset_and_restore() that scales up the clocks be serialized
> > against ufshcd_clkscale_enable_store()?
>
> Both check and set paths are serialized by hba->host_sem currently.
>
> Would I miss any other unserialized paths?

Where in ufshcd_host_reset_and_restore() or in its callers is 
hba->host_sem obtained? I don't see it. Am I perhaps overlooking something?

Thanks,

Bart.