From: Xiang Chen chenxiang66@hisilicon.com
commit d12544fb2aa9944b180c35914031a8384ab082c1 upstream.
To support runtime PM for hisi SAS driver (the driver is in directory drivers/scsi/hisi_sas), we add device link between scsi_device->sdev_gendev (consumer device) and hisi_hba->dev(supplier device) with flags DL_FLAG_PM_RUNTIME | DL_FLAG_RPM_ACTIVE.
After runtime suspended consumers and supplier, unload the dirver which causes a hung.
We found that it called function device_release_driver_internal() to release the supplier device (hisi_hba->dev), as the device link was busy, it set the device link state to DL_STATE_SUPPLIER_UNBIND, and then it called device_release_driver_internal() to release the consumer device (scsi_device->sdev_gendev).
Then it would try to call pm_runtime_get_sync() to resume the consumer device, but because consumer-supplier relation existed, it would try to resume the supplier first, but as the link state was already DL_STATE_SUPPLIER_UNBIND, so it skipped resuming the supplier and only resumed the consumer which hanged (it sends IOs to resume scsi_device while the SAS controller is suspended).
Simple flow is as follows:
device_release_driver_internal -> (supplier device) if device_links_busy -> device_links_unbind_consumers -> ... WRITE_ONCE(link->status, DL_STATE_SUPPLIER_UNBIND) device_release_driver_internal (consumer device) pm_runtime_get_sync -> (consumer device) ... __rpm_callback -> rpm_get_suppliers -> if link->state == DL_STATE_SUPPLIER_UNBIND -> skip the action of resuming the supplier ... pm_runtime_clean_up_links ...
Correct suspend/resume ordering between a supplier device and its consumer devices (resume the supplier device before resuming consumer devices, and suspend consumer devices before suspending the supplier device) should be guaranteed by runtime PM, but the state checks in rpm_get_supplier() and rpm_put_supplier() break this rule, so remove them.
Signed-off-by: Xiang Chen chenxiang66@hisilicon.com [ rjw: Subject and changelog edits ] Cc: All applicable stable@vger.kernel.org Signed-off-by: Rafael J. Wysocki rafael.j.wysocki@intel.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- drivers/base/power/runtime.c | 5 +---- 1 file changed, 1 insertion(+), 4 deletions(-)
--- a/drivers/base/power/runtime.c +++ b/drivers/base/power/runtime.c @@ -291,8 +291,7 @@ static int rpm_get_suppliers(struct devi device_links_read_lock_held()) { int retval;
- if (!(link->flags & DL_FLAG_PM_RUNTIME) || - READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND) + if (!(link->flags & DL_FLAG_PM_RUNTIME)) continue;
retval = pm_runtime_get_sync(link->supplier); @@ -312,8 +311,6 @@ static void rpm_put_suppliers(struct dev
list_for_each_entry_rcu(link, &dev->links.suppliers, c_node, device_links_read_lock_held()) { - if (READ_ONCE(link->status) == DL_STATE_SUPPLIER_UNBIND) - continue;
while (refcount_dec_not_one(&link->rpm_active)) pm_runtime_put(link->supplier);