Commit 88737106 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
Browse files

PM: runtime: Fix supplier device management during consumer probe 



Because pm_runtime_get_suppliers() bumps up the rpm_active counter
of each device link to a supplier of the given device in addition
to bumping up the supplier's PM-runtime usage counter, a runtime
suspend of the consumer device may case the latter to go down to 0
when pm_runtime_put_suppliers() is running on a remote CPU.  If that
happens after pm_runtime_put_suppliers() has released power.lock for
the consumer device, and a runtime resume of that device takes place
immediately after it, before pm_runtime_put() is called for the
supplier, that pm_runtime_put() call may cause the supplier to be
suspended even though the consumer is active.

To prevent that from happening, modify pm_runtime_get_suppliers() to
call pm_runtime_get_sync() for the given device's suppliers without
touching the rpm_active counters of the involved device links
Accordingly, modify pm_runtime_put_suppliers() to call pm_runtime_put()
for the given device's suppliers without looking at the rpm_active
counters of the device links at hand.  [This is analogous to what
happened before commit 4c06c4e6 ("driver core: Fix possible
supplier PM-usage counter imbalance").]

Since pm_runtime_get_suppliers() sets supplier_preactivated for each
device link where the supplier's PM-runtime usage counter has been
incremented and pm_runtime_put_suppliers() calls pm_runtime_put() for
the suppliers whose device links have supplier_preactivated set, the
PM-runtime usage counter is balanced for each supplier and this is
independent of the runtime suspend and resume of the consumer device.

However, in case a device link with DL_FLAG_PM_RUNTIME set is dropped
during the consumer device probe, so pm_runtime_get_suppliers() bumps
up the supplier's PM-runtime usage counter, but it cannot be dropped by
pm_runtime_put_suppliers(), make device_link_release_fn() take care of
that.

Fixes: 4c06c4e6 ("driver core: Fix possible supplier PM-usage counter imbalance")
Reported-by: default avatarPeter Wang <peter.wang@mediatek.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: default avatarPeter Wang <peter.wang@mediatek.com>
Cc: 5.1+ <stable@vger.kernel.org> # 5.1+
parent 07358194

drivers/base/core.c

+10 −0
Original line number Diff line number Diff line
@@ -487,6 +487,16 @@ static void device_link_release_fn(struct work_struct *work) 
	device_link_synchronize_removal();



	pm_runtime_release_supplier(link);

	/*

	 * If supplier_preactivated is set, the link has been dropped between

	 * the pm_runtime_get_suppliers() and pm_runtime_put_suppliers() calls

	 * in __driver_probe_device().  In that case, drop the supplier's

	 * PM-runtime usage counter to remove the reference taken by

	 * pm_runtime_get_suppliers().

	 */

	if (link->supplier_preactivated)

		pm_runtime_put_noidle(link->supplier);



	pm_request_idle(link->supplier);



	put_device(link->consumer);

drivers/base/power/runtime.c

+1 −13
Original line number Diff line number Diff line
@@ -1768,7 +1768,6 @@ void pm_runtime_get_suppliers(struct device *dev) 
		if (link->flags & DL_FLAG_PM_RUNTIME) {

			link->supplier_preactivated = true;

			pm_runtime_get_sync(link->supplier);

			refcount_inc(&link->rpm_active);

		}



	device_links_read_unlock(idx);
@@ -1788,18 +1787,7 @@ void pm_runtime_put_suppliers(struct device *dev) 
	list_for_each_entry_rcu(link, &dev->links.suppliers, c_node,

				device_links_read_lock_held())

		if (link->supplier_preactivated) {

			bool put;



			link->supplier_preactivated = false;



			spin_lock_irq(&dev->power.lock);



			put = pm_runtime_status_suspended(dev) &&

			      refcount_dec_not_one(&link->rpm_active);



			spin_unlock_irq(&dev->power.lock);



			if (put)

			pm_runtime_put(link->supplier);

		}