linux-kernel - Re: [PATCH] scsi: ufs: fix livelock of ufshcd_clear_ua

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Message-ID: <X+DZMwSHsskcEgZE@google.com>
Date:   Mon, 21 Dec 2020 09:19:47 -0800
From:   Jaegeuk Kim <jaegeuk@...nel.org>
To:     Avri Altman <Avri.Altman@....com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "kernel-team@...roid.com" <kernel-team@...roid.com>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "stanley.chu@...iatek.com" <stanley.chu@...iatek.com>
Subject: Re: [PATCH] scsi: ufs: fix livelock of ufshcd_clear_ua_wluns

On 12/21, Avri Altman wrote:
> > > > When gate_work/ungate_work gets an error during hibern8_enter or
> > exit,
> > > >  ufshcd_err_handler()
> > > >    ufshcd_scsi_block_requests()
> > > >    ufshcd_reset_and_restore()
> > > >      ufshcd_clear_ua_wluns() -> stuck
> > > >    ufshcd_scsi_unblock_requests()
> > > >
> > > > In order to avoid it, ufshcd_clear_ua_wluns() can be called per recovery
> > > > flows
> > > > such as suspend/resume, link_recovery, and error_handler.
> > > Not sure that suspend/resume are UAC events?
> > 
> > Could you elaborate a bit? The goal is to clear UAC after UFS reset happens.
> So why calling it on every suspend and resume?

1. If UAC was cleared, there's no impact. 
2. ufshcd_link_recovery() can reset UFS directly by ufs_mtk_resume().
3. ufshcd_suspend can call ufshcd_host_reset_and_restore() as well.

> 
> > 
> > >
> > > Also the 'fixes' tag is missing.
> > 
> > Added. Thanks,
> > 
> > >
> > > Thanks,
> > > Avri