linux-kernel - Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB on/off

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Date:   Tue, 22 Dec 2020 21:50:49 +0100
From:   Bean Huo <huobean@...il.com>
To:     Stanley Chu <stanley.chu@...iatek.com>
Cc:     alim.akhtar@...sung.com, avri.altman@....com,
        asutoshd@...eaurora.org, jejb@...ux.ibm.com,
        martin.petersen@...cle.com, beanhuo@...ron.com, bvanassche@....org,
        tomas.winkler@...el.com, cang@...eaurora.org,
        linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 1/7] scsi: ufs: Add "wb_on" sysfs node to control WB
 on/off

On Tue, 2020-12-22 at 14:08 +0800, Stanley Chu wrote:
> > +     if (kstrtouint(buf, 0, &wb_enable))
> > +             return -EINVAL;
> > +
> > +     if (wb_enable != 0 && wb_enable != 1)
> > +             return -EINVAL;
> > +
> > +     pm_runtime_get_sync(hba->dev);
> > +     res = ufshcd_wb_ctrl(hba, wb_enable);
> 
> May this operation race with UFS shutdown flow?
> 
> To be more clear, ufshcd_wb_ctrl() here may be executed after host
> clock
> is disabled by shutdown flow?
> 
> If yes, we need to avoid it.
> 
> Thanks,
> Stanley Chu

Yes, it is quite possible, but who will mess up this on purpose?

ok, to counterbalance our concerns, I can add checkup:


/* UFS device & link must be active before we change WB status */
if (!ufshcd_is_ufs_dev_active(hba) || !ufshcd_is_link_active(hba))
	return -EINVAL;


how do you think about?

Bean