linux-kernel - Re: [PATCH v2 1/1] scsi: pm: Balance pm_only counter of request queue during system resume

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Date:   Tue, 14 Apr 2020 14:14:25 +0800
From:   Can Guo <cang@...eaurora.org>
To:     asutoshd@...eaurora.org, nguyenb@...eaurora.org,
        hongwus@...eaurora.org, rnayak@...eaurora.org,
        linux-scsi@...r.kernel.org, kernel-team@...roid.com,
        saravanak@...gle.com, salyzyn@...gle.com, cang@...eaurora.org
Cc:     "James E.J. Bottomley" <jejb@...ux.ibm.com>,
        "Martin K. Petersen" <martin.petersen@...cle.com>,
        Stanley Chu <stanley.chu@...iatek.com>,
        Alim Akhtar <alim.akhtar@...sung.com>,
        Avri Altman <avri.altman@....com>,
        "Bean Huo (beanhuo)" <beanhuo@...ron.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] scsi: pm: Balance pm_only counter of request queue
 during system resume

Loop more...

On 2020-04-14 13:24, 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.
> 
> (struct request_queue)0xFFFFFF815B69E938
> 	pm_only = (counter = 2),
> 	rpm_status = 0,
> 	dev = 0xFFFFFF815B0511A0,
> 
> ((struct device)0xFFFFFF815B0511A0)).power
> 	is_suspended = FALSE,
> 	runtime_status = RPM_ACTIVE,
> 
> (struct scsi_device)0xffffff815b051000
> 	request_queue = 0xFFFFFF815B69E938,
> 	sdev_state = SDEV_RUNNING,
> 	quiesced_by = 0x0,
> 
> B::v.f_/task_0xFFFFFF810C246940
> -000|__switch_to(prev = 0xFFFFFF810C246940, next = 0xFFFFFF80A49357C0)
> -001|context_switch(inline)
> -001|__schedule(?)
> -002|schedule()
> -003|blk_queue_enter(q = 0xFFFFFF815B69E938, flags = 0)
> -004|generic_make_request(?)
> -005|submit_bio(bio = 0xFFFFFF80A8195B80)
> 
> Signed-off-by: Can Guo <cang@...eaurora.org>
> 
> Change since v1:
> - Added more debugging context info
> 
> ---
>  drivers/scsi/scsi_pm.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/scsi/scsi_pm.c b/drivers/scsi/scsi_pm.c
> index 3717eea..4804029 100644
> --- a/drivers/scsi/scsi_pm.c
> +++ b/drivers/scsi/scsi_pm.c
> @@ -93,8 +93,10 @@ 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 (blk_queue_pm_only(sdev->request_queue))
> +				blk_post_runtime_resume(sdev->request_queue, 0);
> +			else
> +				blk_set_runtime_active(sdev->request_queue);
>  		}
>  	}