From: Martin Kepplinger <martin.kepplinger@puri.sm>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Bart Van Assche <bvanassche@acm.org>,
jejb@linux.ibm.com, Can Guo <cang@codeaurora.org>,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
linux-kernel@vger.kernel.org, kernel@puri.sm
Subject: Re: [PATCH] scsi: sd: add runtime pm to open / release
Date: Thu, 30 Jul 2020 10:05:50 +0200 [thread overview]
Message-ID: <c253dde7-9347-b3dc-9c91-65d685793b29@puri.sm> (raw)
In-Reply-To: <20200629161536.GA405175@rowland.harvard.edu>
On 29.06.20 18:15, Alan Stern wrote:
> On Mon, Jun 29, 2020 at 11:42:59AM +0200, Martin Kepplinger wrote:
>>
>>
>> On 26.06.20 17:44, Alan Stern wrote:
>>> Martin's best approach would be to add some debugging code to find out why
>>> blk_queue_enter() isn't calling bkl_pm_request_resume(), or why that call
>>> doesn't lead to pm_request_resume().
>>>
>>> Alan Stern
>>>
>>
>> Hi Alan,
>>
>> blk_queue_enter() always - especially when sd is runtime suspended and I
>> try to mount as above - sets success to be true for me, so never
>> continues down to bkl_pm_request_resume(). All I see is "PM: Removing
>> info for No Bus:sda1".
>
> Aha. Looking at this more closely, it's apparent that the code in
> blk-core.c contains a logic bug: It assumes that if the BLK_MQ_REQ_PREEMPT
> flag is set then the request can be issued regardless of the queue's
> runtime status. That is not correct when the queue is suspended.
>
> Below is my attempt to fix this up. I'm not sure that the patch is
> entirely correct, but it should fix this logic bug. I would appreciate a
> critical review.
>
> Martin, does this fix the problem?
>
> Alan Stern
Hi Alan,
So in the block layer your change below indeed fixes the problem and if
you want to submit that 1:1 feel free to add
Tested-by: Martin Kepplinger <martin.kepplinger@puri.sm>
thanks for your help in this!
martin
>
>
>
> Index: usb-devel/block/blk-core.c
> ===================================================================
> --- usb-devel.orig/block/blk-core.c
> +++ usb-devel/block/blk-core.c
> @@ -423,7 +423,8 @@ int blk_queue_enter(struct request_queue
> * responsible for ensuring that that counter is
> * globally visible before the queue is unfrozen.
> */
> - if (pm || !blk_queue_pm_only(q)) {
> + if ((pm && q->rpm_status != RPM_SUSPENDED) ||
> + !blk_queue_pm_only(q)) {
> success = true;
> } else {
> percpu_ref_put(&q->q_usage_counter);
> @@ -448,8 +449,7 @@ int blk_queue_enter(struct request_queue
>
> wait_event(q->mq_freeze_wq,
> (!q->mq_freeze_depth &&
> - (pm || (blk_pm_request_resume(q),
> - !blk_queue_pm_only(q)))) ||
> + blk_pm_resume_queue(pm, q)) ||
> blk_queue_dying(q));
> if (blk_queue_dying(q))
> return -ENODEV;
> Index: usb-devel/block/blk-pm.h
> ===================================================================
> --- usb-devel.orig/block/blk-pm.h
> +++ usb-devel/block/blk-pm.h
> @@ -6,11 +6,14 @@
> #include <linux/pm_runtime.h>
>
> #ifdef CONFIG_PM
> -static inline void blk_pm_request_resume(struct request_queue *q)
> +static inline int blk_pm_resume_queue(const bool pm, struct request_queue *q)
> {
> - if (q->dev && (q->rpm_status == RPM_SUSPENDED ||
> - q->rpm_status == RPM_SUSPENDING))
> - pm_request_resume(q->dev);
> + if (!q->dev || !blk_queue_pm_only(q))
> + return 1; /* Nothing to do */
> + if (pm && q->rpm_status != RPM_SUSPENDED)
> + return 1; /* Request allowed */
> + pm_request_resume(q->dev);
> + return 0;
> }
>
> static inline void blk_pm_mark_last_busy(struct request *rq)
> @@ -44,8 +47,9 @@ static inline void blk_pm_put_request(st
> --rq->q->nr_pending;
> }
> #else
> -static inline void blk_pm_request_resume(struct request_queue *q)
> +static inline int blk_pm_resume_queue(const bool pm, struct request_queue *q)
> {
> + return 1;
> }
>
> static inline void blk_pm_mark_last_busy(struct request *rq)
>
next prev parent reply other threads:[~2020-07-30 8:06 UTC|newest]
Thread overview: 68+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-23 11:10 [PATCH] scsi: sd: add runtime pm to open / release Martin Kepplinger
2020-06-24 13:33 ` Bart Van Assche
2020-06-25 8:16 ` Martin Kepplinger
2020-06-25 14:52 ` Alan Stern
2020-06-26 3:53 ` Bart Van Assche
2020-06-26 15:07 ` Bart Van Assche
2020-06-26 15:44 ` Alan Stern
2020-06-28 2:37 ` Bart Van Assche
2020-06-28 13:10 ` Alan Stern
2020-06-29 9:42 ` Martin Kepplinger
2020-06-29 16:15 ` Alan Stern
2020-06-29 16:56 ` Bart Van Assche
2020-06-29 17:40 ` Alan Stern
2020-06-30 3:33 ` Martin Kepplinger
2020-06-30 13:38 ` Alan Stern
2020-06-30 15:59 ` Bart Van Assche
2020-06-30 18:02 ` Alan Stern
2020-06-30 19:23 ` Bart Van Assche
2020-06-30 19:38 ` Alan Stern
2020-06-30 23:31 ` Bart Van Assche
2020-07-01 0:49 ` Alan Stern
2020-07-06 16:41 ` Alan Stern
2020-07-28 7:02 ` Martin Kepplinger
2020-07-28 20:02 ` Alan Stern
2020-07-29 14:12 ` Martin Kepplinger
2020-07-29 14:32 ` Alan Stern
2020-07-29 14:44 ` Martin K. Petersen
2020-07-29 14:56 ` Alan Stern
2020-07-29 14:46 ` James Bottomley
2020-07-29 14:53 ` James Bottomley
2020-07-29 15:40 ` Martin Kepplinger
2020-07-29 15:44 ` James Bottomley
2020-07-29 16:43 ` Martin Kepplinger
2020-07-29 18:25 ` Alan Stern
2020-07-29 18:29 ` James Bottomley
2020-07-30 8:52 ` Martin Kepplinger
2020-07-30 8:54 ` Martin Kepplinger
2020-07-30 15:10 ` Alan Stern
2020-08-04 9:39 ` Martin Kepplinger
2020-08-07 9:51 ` Martin Kepplinger
2020-08-07 14:30 ` Alan Stern
2020-08-08 6:59 ` Martin Kepplinger
2020-08-08 15:05 ` Alan Stern
2020-08-09 9:20 ` Martin Kepplinger
2020-08-09 15:26 ` Alan Stern
2020-08-10 12:03 ` Martin Kepplinger
2020-08-10 14:13 ` Alan Stern
2020-08-11 7:55 ` Martin Kepplinger
2020-08-11 13:48 ` Alan Stern
2020-08-23 14:57 ` [PATCH] block: Fix bug in runtime-resume handling Alan Stern
2020-08-24 17:48 ` Bart Van Assche
2020-08-24 20:13 ` Alan Stern
2020-08-26 7:48 ` Martin Kepplinger
2020-08-27 17:42 ` Martin Kepplinger
2020-08-27 20:29 ` Alan Stern
2020-08-29 7:24 ` Martin Kepplinger
2020-08-29 15:26 ` Alan Stern
2020-08-29 16:33 ` Martin Kepplinger
2020-08-29 18:56 ` Alan Stern
2020-08-30 0:38 ` Bart Van Assche
2020-08-30 1:06 ` Alan Stern
2020-07-29 15:40 ` [PATCH] scsi: sd: add runtime pm to open / release Alan Stern
2020-07-29 15:49 ` James Bottomley
2020-07-29 16:17 ` Alan Stern
2020-07-29 15:52 ` Martin Kepplinger
2020-07-29 18:10 ` Douglas Gilbert
2020-07-30 8:05 ` Martin Kepplinger [this message]
2020-07-30 15:14 ` Alan Stern
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