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: <2356ab42-bbdd-d214-30f5-a533fe978dcb@acm.org>
Date:   Fri, 1 May 2020 10:56:00 -0700
From:   Bart Van Assche <bvanassche@....org>
To:     Can Guo <cang@...eaurora.org>
Cc:     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,
        "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 2020-04-30 22:12, Can Guo wrote:
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index 3717eea..d18271d 100644
> --- a/drivers/scsi/scsi_pm.c
> +++ b/drivers/scsi/scsi_pm.c
> @@ -74,12 +74,15 @@ static int scsi_dev_type_resume(struct device *dev,
>  {
>         const struct dev_pm_ops *pm = dev->driver ? dev->driver->pm : NULL;
>         int err = 0;
> +       bool was_rpm_suspended = false;
> 
>         err = cb(dev, pm);
>         scsi_device_resume(to_scsi_device(dev));
>         dev_dbg(dev, "scsi resume: %d\n", err);
> 
>         if (err == 0) {
> +               was_rpm_suspended = pm_runtime_suspended(dev);
> +

How about renaming this variable into "was_runtime_suspended"? How about
moving the declaration of that variable inside the if-statement?

>                 pm_runtime_disable(dev);
>                 err = pm_runtime_set_active(dev);
>                 pm_runtime_enable(dev);
> @@ -93,8 +96,10 @@ static int scsi_dev_type_resume(struct device *dev,
>                  */
>                 if (!err && scsi_is_sdev_device(dev)) {
>                         struct scsi_device *sdev = to_scsi_device(dev);
> -
> -                       blk_set_runtime_active(sdev->request_queue);
> +                       if (was_rpm_suspended)
> +                              blk_post_runtime_resume(sdev->request_queue, 0);
> +                       else
> +                              blk_set_runtime_active(sdev->request_queue);
>                 }
>         }

Does other code always call both blk_pre_runtime_resume() and
blk_post_runtime_resume() upon runtime resume? How about adding a
blk_pre_runtime_resume() call before the blk_post_runtime_resume() call?

Thanks,

Bart.