linux-kernel - Re: [PATCH v1] scsi: ufs: Fix ufshcd_scale

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Message-ID: <CAGaU9a_G1kH8VezozhZ3-S6-GvMr=EUVc4btU8Dwdo+cCJDxUg@mail.gmail.com>
Date:   Sat, 30 Jul 2022 15:08:05 +0800
From:   Stanley Chu <chu.stanley@...il.com>
To:     Bart Van Assche <bvanassche@....org>
Cc:     Stanley Chu <stanley.chu@...iatek.com>, linux-scsi@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        "Martin K . Petersen" <martin.petersen@...cle.com>,
        Avri Altman <avri.altman@....com>, alim.akhtar@...sung.com,
        "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        peter.wang@...iatek.com, Chun-Hung Wu <chun-hung.wu@...iatek.com>,
        alice.chao@...iatek.com, powen.kao@...iatek.com,
        mason.zhang@...iatek.com, qilin.tan@...iatek.com,
        lin.gui@...iatek.com, eddie.huang@...iatek.com,
        tun-yu.yu@...iatek.com, cc.chou@...iatek.com,
        chaotian.jing@...iatek.com, jiajie.hao@...iatek.com
Subject: Re: [PATCH v1] scsi: ufs: Fix ufshcd_scale_clks decision in recovery flow

Hi Bart,

On Sat, Jul 30, 2022 at 4:12 AM Bart Van Assche <bvanassche@....org> 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)