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

[Stanley Chu]

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?

Thanks,
Stanley


>
> Thanks,
>
> Bart.



-- 
Yours truly,

朱原陞 (Stanley Chu)