On Tue, Jun 30, 2020 at 11:17:34AM -0400, 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.
>
> This patch simplifies the situation considerably by adding the missing
> function call directly into blk_set_runtime_active(). 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@xxxxxxxxxxxxxxxxxxx>
> CC: Can Guo <cang@xxxxxxxxxxxxxx>
> CC: Bart Van Assche <bvanassche@xxxxxxx>
Please disregard this patch. When I wrote it, I didn't realize that
blk_clear_pm_only() is meant to be used like a reference counter (it's a
bad choice of name, since the routine does a decrement rather than a
clear -- and likewise for blk_set_pm_only()).
I'll submit a revised patch later.
Alan Stern
> block/blk-pm.c | 25 ++++++++++---------------
> drivers/scsi/scsi_pm.c | 10 ++--------
> 2 files changed, 12 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);
>
> @@ -204,6 +195,9 @@ 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)
> {
> @@ -213,6 +207,7 @@ void blk_set_runtime_active(struct reque
> pm_runtime_mark_last_busy(q->dev);
> pm_request_autosuspend(q->dev);
> spin_unlock_irq(&q->queue_lock);
> + 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);
> }
> }
>
>
