Re: [PATCH v1] PM-runtime: Check supplier_preactivated before release supplier
From: Peter Wang
Date: Tue Aug 02 2022 - 09:33:26 EST
On 8/2/22 7:01 PM, Rafael J. Wysocki wrote:
On Tue, Aug 2, 2022 at 5:19 AM Peter Wang <peter.wang@xxxxxxxxxxxx> wrote:
Hi Rafael,
Yes, it is very clear!
I miss this important key point that usage_count is always >
rpm_active 1.
I think this patch could work.
Thanks.
Peter
Hi Rafael,
After test with commit ("887371066039011144b4a94af97d9328df6869a2 PM:
runtime: Fix supplier device management during consumer probe") past weeks,
The supplier still suspend when consumer is active "after"
pm_runtime_put_suppliers.
Do you have any idea about that?
Well, this means that the consumer probe doesn't bump up the
supplier's PM-runtime usage counter as appropriate.
You need to tell me more about what happens during the consumer probe.
Which driver is this?
Hi Rafael,
I have the same idea with you. But I still don't know how it could happen.
It is upstream ufs driver in scsi system. Here is call flow
do_scan_async (process 1)
do_scsi_scan_host
scsi_scan_host_selected
scsi_scan_channel
__scsi_scan_target
scsi_probe_and_add_lun
scsi_alloc_sdev
slave_alloc -> setup link
scsi_add_lun
slave_configure -> enable rpm
scsi_sysfs_add_sdev
scsi_autopm_get_device <- get runtime pm
device_add <- invoke
sd_probe in process 2
scsi_autopm_put_device <- put
runtime pm, point 1
driver_probe_device (process 2)
__driver_probe_device
pm_runtime_get_suppliers
really_probe
sd_probe
scsi_autopm_get_device <- get
runtime pm, point 2
pm_runtime_set_autosuspend_delay <- set rpm
delay to 2s
scsi_autopm_put_device <- put
runtime pm
pm_runtime_put_suppliers <-
(link->rpm_active = 1)
After process 1 call scsi_autopm_put_device(point 1) let consumer enter
suspend,
process 2 call scsi_autopm_get_device(point 2) may have chance resume
consumer but not
bump up the supplier's PM-runtime usage counter as appropriate.
Thanks.
Peter