From: Can Guo <cang@codeaurora.org>
To: Alan Stern <stern@rowland.harvard.edu>
Cc: Bart Van Assche <bvanassche@acm.org>,
martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
linux-block@vger.kernel.org
Subject: Re: [PATCH v2] SCSI and block: Simplify resume handling
Date: Wed, 22 Jul 2020 09:46:10 +0800 [thread overview]
Message-ID: <d2605929ee63b3a2386bc01965202950@codeaurora.org> (raw)
In-Reply-To: <20200701183718.GA507293@rowland.harvard.edu>
Hi Alan,
On 2020-07-02 02:37, Alan Stern wrote:
> Commit 05d18ae1cc8a ("scsi: pm: Balance pm_only counter of request
> queue during system resume") fixed a problem in the block layer's
> runtime-PM code: blk_set_runtime_active() failed to call
> blk_clear_pm_only(). However, the commit's implementation was
> awkward; it forced the SCSI system-resume handler to choose whether to
> call blk_post_runtime_resume() or blk_set_runtime_active(), depending
> on whether or not the SCSI device had previously been runtime
> suspended.
>
Yeah, even I thoght it was awkward as I couldn't find a way or a
existing
API to fix it subtly without changing block layer. I was trying not to
make noise to block layer as I am not an expert of it, so I chose the
akward
way to keep the fix within driver layer. Anyways, thanks for the change
and
I will come back after I test it.
Can Guo.
> This patch simplifies the situation considerably by adding the missing
> function call directly into blk_set_runtime_active() (under the
> condition that the queue is not already in the RPM_ACTIVE state).
> This allows the SCSI routine to revert back to its original form.
> Furthermore, making this change reveals that blk_post_runtime_resume()
> (in its success pathway) does exactly the same thing as
> blk_set_runtime_active(). The duplicate code is easily removed by
> making one routine call the other.
>
> No functional changes are intended.
>
> Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
> CC: Can Guo <cang@codeaurora.org>
> CC: Bart Van Assche <bvanassche@acm.org>
>
> ---
>
> v2: Don't call blk_clear_pm_only() if the queue's RPM status was
> already set to RPM_ACTIVE. This happens during a system resume
> if the device was not in runtime suspend beforehand.
>
> Martin:
>
> Since you merged the oritinal 05d18ae1cc8a commit, I'm submitting this
> to
> you as an update. If you would prefer to have it go by way of the
> block-layer tree, let me know and I'll resend it.
>
>
> [as1939b]
>
>
> block/blk-pm.c | 30 +++++++++++++++---------------
> drivers/scsi/scsi_pm.c | 10 ++--------
> 2 files changed, 17 insertions(+), 23 deletions(-)
>
> Index: usb-devel/block/blk-pm.c
> ===================================================================
> --- usb-devel.orig/block/blk-pm.c
> +++ usb-devel/block/blk-pm.c
> @@ -164,30 +164,21 @@ EXPORT_SYMBOL(blk_pre_runtime_resume);
> *
> * Description:
> * Update the queue's runtime status according to the return value
> of the
> - * device's runtime_resume function. If it is successfully resumed,
> process
> - * the requests that are queued into the device's queue when it is
> resuming
> - * and then mark last busy and initiate autosuspend for it.
> + * device's runtime_resume function. If the resume was successful,
> call
> + * blk_set_runtime_active() to do the real work of restarting the
> queue.
> *
> * This function should be called near the end of the device's
> * runtime_resume callback.
> */
> void blk_post_runtime_resume(struct request_queue *q, int err)
> {
> - if (!q->dev)
> - return;
> -
> - spin_lock_irq(&q->queue_lock);
> if (!err) {
> - q->rpm_status = RPM_ACTIVE;
> - pm_runtime_mark_last_busy(q->dev);
> - pm_request_autosuspend(q->dev);
> - } else {
> + blk_set_runtime_active(q);
> + } else if (q->dev) {
> + spin_lock_irq(&q->queue_lock);
> q->rpm_status = RPM_SUSPENDED;
> + spin_unlock_irq(&q->queue_lock);
> }
> - spin_unlock_irq(&q->queue_lock);
> -
> - if (!err)
> - blk_clear_pm_only(q);
> }
> EXPORT_SYMBOL(blk_post_runtime_resume);
>
> @@ -204,15 +195,24 @@ EXPORT_SYMBOL(blk_post_runtime_resume);
> * This function can be used in driver's resume hook to correct queue
> * runtime PM status and re-enable peeking requests from the queue. It
> * should be called before first request is added to the queue.
> + *
> + * This function is also called by blk_post_runtime_resume() for
> successful
> + * runtime resumes. It does everything necessary to restart the
> queue.
> */
> void blk_set_runtime_active(struct request_queue *q)
> {
> if (q->dev) {
> + int old_status;
> +
> spin_lock_irq(&q->queue_lock);
> + old_status = q->rpm_status;
> q->rpm_status = RPM_ACTIVE;
> pm_runtime_mark_last_busy(q->dev);
> pm_request_autosuspend(q->dev);
> spin_unlock_irq(&q->queue_lock);
> +
> + if (old_status != RPM_ACTIVE)
> + blk_clear_pm_only(q);
> }
> }
> EXPORT_SYMBOL(blk_set_runtime_active);
> Index: usb-devel/drivers/scsi/scsi_pm.c
> ===================================================================
> --- usb-devel.orig/drivers/scsi/scsi_pm.c
> +++ usb-devel/drivers/scsi/scsi_pm.c
> @@ -80,10 +80,6 @@ static int scsi_dev_type_resume(struct d
> dev_dbg(dev, "scsi resume: %d\n", err);
>
> if (err == 0) {
> - bool was_runtime_suspended;
> -
> - was_runtime_suspended = pm_runtime_suspended(dev);
> -
> pm_runtime_disable(dev);
> err = pm_runtime_set_active(dev);
> pm_runtime_enable(dev);
> @@ -97,10 +93,8 @@ static int scsi_dev_type_resume(struct d
> */
> if (!err && scsi_is_sdev_device(dev)) {
> struct scsi_device *sdev = to_scsi_device(dev);
> - if (was_runtime_suspended)
> - blk_post_runtime_resume(sdev->request_queue, 0);
> - else
> - blk_set_runtime_active(sdev->request_queue);
> +
> + blk_set_runtime_active(sdev->request_queue);
> }
> }
prev parent reply other threads:[~2020-07-22 1:46 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-01 18:37 [PATCH v2] SCSI and block: Simplify resume handling Alan Stern
2020-07-06 2:41 ` Bart Van Assche
2020-07-06 15:14 ` [PATCH v3] " Alan Stern
2020-07-09 3:29 ` Bart Van Assche
2020-07-21 3:01 ` Martin K. Petersen
2020-07-23 3:53 ` Bart Van Assche
2020-07-25 2:50 ` Martin K. Petersen
2020-07-22 1:46 ` Can Guo [this message]
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