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

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Message-ID: <DM6PR04MB657558D8353199D53586F654FCC00@DM6PR04MB6575.namprd04.prod.outlook.com>
Date:   Mon, 21 Dec 2020 18:05:15 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Jaegeuk Kim <jaegeuk@...nel.org>
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.
But the command is still sent.

> 2. ufshcd_link_recovery() can reset UFS directly by ufs_mtk_resume().
> 3. ufshcd_suspend can call ufshcd_host_reset_and_restore() as well.
Seems excessive IMO.
Why not selectively send when indeed required, e.g. on reset?