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@xxxxxxxxxxxxxxxxxxx>
CC: Can Guo <cang@xxxxxxxxxxxxxx>
CC: Bart Van Assche <bvanassche@xxxxxxx>
---
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);
}
}
