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From: Alan Stern <stern@rowland.harvard.edu>
To: Bart Van Assche <bvanassche@acm.org>, martin.petersen@oracle.com
Cc: Can Guo <cang@codeaurora.org>,
	linux-scsi@vger.kernel.org, linux-block@vger.kernel.org
Subject: [PATCH] SCSI and block: Simplify resume handling
Date: Tue, 30 Jun 2020 11:17:34 -0400	[thread overview]
Message-ID: <20200630151734.GA451991@rowland.harvard.edu> (raw)

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@rowland.harvard.edu>
CC: Can Guo <cang@codeaurora.org>
CC: Bart Van Assche <bvanassche@acm.org>

---

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.


[as1939]


 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);
 		}
 	}
 


             reply	other threads:[~2020-06-30 15:17 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-30 15:17 Alan Stern [this message]
2020-07-01  1:08 ` Alan Stern

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