linux-kernel - RE: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in ufshcd_err_handling

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Date: Tue, 23 Jan 2024 11:38:30 +0900
From: "hoyoung seo" <hy50.seo@...sung.com>
To: "'Bart Van Assche'" <bvanassche@....org>, <linux-scsi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <alim.akhtar@...sung.com>,
	<avri.altman@....com>, <jejb@...ux.ibm.com>, <martin.petersen@...cle.com>,
	<beanhuo@...ron.com>, <kwangwon.min@...sung.com>, <kwmad.kim@...sung.com>,
	<sh425.lee@...sung.com>, <sc.suh@...sung.com>, <quic_nguyenb@...cinc.com>,
	<cpgs@...sung.com>, <grant.jung@...sung.com>, <junwoo80.lee@...sung.com>
Subject: RE: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in
 ufshcd_err_handling_prepare

> -----Original Message-----
> From: Bart Van Assche <bvanassche@....org>
> Sent: Tuesday, January 23, 2024 5:37 AM
> To: SEO HOYOUNG <hy50.seo@...sung.com>; linux-scsi@...r.kernel.org; linux-
> kernel@...r.kernel.org; alim.akhtar@...sung.com; avri.altman@....com;
> jejb@...ux.ibm.com; martin.petersen@...cle.com; beanhuo@...ron.com;
> kwangwon.min@...sung.com; kwmad.kim@...sung.com; sh425.lee@...sung.com;
> sc.suh@...sung.com; quic_nguyenb@...cinc.com; cpgs@...sung.com;
> grant.jung@...sung.com; junwoo80.lee@...sung.com
> Subject: Re: [PATCH v1] scsi: ufs: core: Remove the ufshcd_release in
> ufshcd_err_handling_prepare
> 
> On 1/22/24 00:33, SEO HOYOUNG wrote:
> > If err_handler is performed in the suspend/resume situation,
> > ufs_release can be called twice and active_reqs valid can be negative.
> > This is because ufshcd_errhandling_prepare() and
> > ufshcd_err_handling_unprepare() repeatedly release calls.
> > Eventually, active_reqs have a value different from the intention.
> > To prevent this, release duplication processing was removed.
> >
> > Signed-off-by: SEO HOYOUNG <hy50.seo@...sung.com>
> > ---
> >   drivers/ufs/core/ufshcd.c | 1 -
> >   1 file changed, 1 deletion(-)
> >
> > diff --git a/drivers/ufs/core/ufshcd.c b/drivers/ufs/core/ufshcd.c
> > index 7c59d7a02243..423e83074a20 100644
> > --- a/drivers/ufs/core/ufshcd.c
> > +++ b/drivers/ufs/core/ufshcd.c
> > @@ -6351,7 +6351,6 @@ static void ufshcd_err_handling_prepare(struct
> ufs_hba *hba)
> >   		ufshcd_hold(hba);
> >   		if (!ufshcd_is_clkgating_allowed(hba))
> >   			ufshcd_setup_clocks(hba, true);
> > -		ufshcd_release(hba);
> >   		pm_op = hba->is_sys_suspended ? UFS_SYSTEM_PM :
> UFS_RUNTIME_PM;
> >   		ufshcd_vops_resume(hba, pm_op);
> >   	} else {
> 
> I think that the above ufshcd_release() call pairs with the ufshcd_hold()
> call three lines above it and hence that removing that call would be wrong.
> 
> Thanks,
> 
> Bart.

Hi,

It was a different when I tested it.
If __ufshcd_wl_resume() is called active_reqs is 1.
Because ufshcd_hold() is called in __ufshcd_wl_suspend().
If occurred hibern8_exit failed in __ufschd_wl_resume(), ufshcd_release()
is called in the :out syntax, and active_reqs becomes 0.
After that, active_reqs becomes 0 because ufshcd_hold() is called 
from ufshcd_err_handling_repare()and ufshcd_release() is called again while
err_handler is operating.
When err_handler is completed, active_reqs becomes negative because 
ufshcd_release() is called again in ufshcd_err_handling_unprepare().
I tested it while printing the log, and if I misanalyzed it, let me know.

Thanks,

SEO.