linux-kernel - RE: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt notification

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Date:   Tue, 14 Jul 2020 09:29:49 +0000
From:   Avri Altman <Avri.Altman@....com>
To:     Stanley Chu <stanley.chu@...iatek.com>
CC:     "linux-scsi@...r.kernel.org" <linux-scsi@...r.kernel.org>,
        "martin.petersen@...cle.com" <martin.petersen@...cle.com>,
        "alim.akhtar@...sung.com" <alim.akhtar@...sung.com>,
        "jejb@...ux.ibm.com" <jejb@...ux.ibm.com>,
        "bvanassche@....org" <bvanassche@....org>,
        "beanhuo@...ron.com" <beanhuo@...ron.com>,
        "asutoshd@...eaurora.org" <asutoshd@...eaurora.org>,
        "cang@...eaurora.org" <cang@...eaurora.org>,
        "matthias.bgg@...il.com" <matthias.bgg@...il.com>,
        "linux-mediatek@...ts.infradead.org" 
        <linux-mediatek@...ts.infradead.org>,
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        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kuohong.wang@...iatek.com" <kuohong.wang@...iatek.com>,
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        "chaotian.jing@...iatek.com" <chaotian.jing@...iatek.com>,
        "cc.chou@...iatek.com" <cc.chou@...iatek.com>
Subject: RE: [PATCH v3] scsi: ufs: Cleanup completed request without interrupt
 notification

> > > > > +cleanup:
> > > > > +       spin_lock_irqsave(host->host_lock, flags);
> > > > > +       if (!test_bit(tag, &hba->outstanding_reqs)) {
> > Is this needed?  it was already checked in line 6439.
> >
> 
> I am worried about the case that interrupt comes very lately. 
scsi timeout is 30sec - do you expect an interrupt to arrive after that?

Thanks,
Avri

>For
> example, if interrupt finally comes while ufshcd_abort() is handling
> this command, then probably this command may be completed first by
> interrupt handler. In this case, ufshcd_abort() shall not clear this
> command again. In contrast, if ufshcd_abort() clears this command first,
> then interrupt shall not complete it. Thus here checking
> hba->outstanding_req with host lock held is required to prevent above
> racing.
> 
> Thanks,
> Stanley Chu
>