linux-kernel - Re: [PATCH v3 1/1] scsi: pm: Balance pm_only counter of request queue during system resume

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Message-ID: <9e15123e-4315-15cd-3d23-2df6144bd376@acm.org>
Date:   Wed, 29 Apr 2020 22:08:48 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>, asutoshd@...eaurora.org,
        nguyenb@...eaurora.org, hongwus@...eaurora.org,
        rnayak@...eaurora.org, stanley.chu@...iatek.com,
        alim.akhtar@...sung.com, beanhuo@...ron.com, Avri.Altman@....com,
        bjorn.andersson@...aro.org, linux-scsi@...r.kernel.org,
        kernel-team@...roid.com, saravanak@...gle.com, salyzyn@...gle.com
Cc:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 1/1] scsi: pm: Balance pm_only counter of request queue
 during system resume

On 2020-04-29 21:10, Can Guo wrote:
> During system resume, scsi_resume_device() decreases a request queue's
> pm_only counter if the scsi device was quiesced before. But after that,
> if the scsi device's RPM status is RPM_SUSPENDED, the pm_only counter is
> still held (non-zero). Current scsi resume hook only sets the RPM status
> of the scsi device and its request queue to RPM_ACTIVE, but leaves the
> pm_only counter unchanged. This may make the request queue's pm_only
> counter remain non-zero after resume hook returns, hence those who are
> waiting on the mq_freeze_wq would never be woken up. Fix this by calling
> blk_post_runtime_resume() if pm_only is non-zero to balance the pm_only
> counter which is held by the scsi device's RPM ops.

How was this issue discovered? How has this patch been tested?

Thanks,

Bart.