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Subject: Re: [PATCH v3 1/1] scsi: pm: Balance pm_only counter of request queue
 during system resume
To:     Can Guo <cang@codeaurora.org>
Cc:     asutoshd@codeaurora.org, nguyenb@codeaurora.org,
        hongwus@codeaurora.org, rnayak@codeaurora.org,
        stanley.chu@mediatek.com, alim.akhtar@samsung.com,
        beanhuo@micron.com, Avri.Altman@wdc.com,
        bjorn.andersson@linaro.org, linux-scsi@vger.kernel.org,
        kernel-team@android.com, saravanak@google.com, salyzyn@google.com,
        "James E.J. Bottomley" <jejb@linux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@oracle.com>,
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From:   Bart Van Assche <bvanassche@acm.org>
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Date:   Thu, 30 Apr 2020 18:50:03 -0700
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On 2020-04-30 18:42, Can Guo wrote:
> On 2020-05-01 04:32, Bart Van Assche wrote:
> > Has it been considered to test directly whether a SCSI device has been
> > runtime suspended instead of relying on blk_queue_pm_only()? How about
> > using pm_runtime_status_suspended() or adding a function in
> > block/blk-pm.h that checks whether q->rpm_status == RPM_SUSPENDED?
> 
> Yes, I used to make the patch like that way, and it also worked well, as
> both ways are equal actually. I kinda like the current code because we
> should be confident that after scsi_dev_type_resume() returns, pm_only
> must be 0. Different reviewers may have different opinions, either way
> works well anyways.

Hi Can,

Please note that this is not a matter of personal preferences of a
reviewer but a matter of correctness. blk_queue_pm_only() does not only
return a value > 0 if a SCSI device has been runtime suspended but also
returns true if scsi_device_quiesce() was called for another reason.
Hence my request to test the "runtime suspended" status directly and not
to rely on blk_queue_pm_only().

Thanks,

Bart.