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 4c06c4e6cf63 ("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: 4c06c4e6cf63 ("driver core: Fix possible supplier PM-usage counter imbalance")
Reported-by: Peter Wang <peter.wang@mediatek.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Peter Wang <peter.wang@mediatek.com>
Cc: 5.1+ <stable@vger.kernel.org> # 5.1+

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 58aa49527d3a..460d6f163e41 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -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);