linux-kernel - [PATCH 3/3] PM: runtime: Resume the device earlier in __device_release

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Date:   Wed, 21 Oct 2020 21:14:18 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Lukas Wunner <lukas@...ner.de>,
        Saravana Kannan <saravanak@...gle.com>,
        Xiang Chen <chenxiang66@...ilicon.com>
Subject: [PATCH 3/3] PM: runtime: Resume the device earlier in __device_release_driver()

From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>

Since the device is resumed from runtime-suspend in
__device_release_driver() anyway, it is better to do that before
looking for busy managed device links from it to consumers, because
if there are any, device_links_unbind_consumers() will be called
and it will cause the consumer devices' drivers to unbind, so the
consumer devices will be runtime-resumed.  In turn, resuming each
consumer device will cause the supplier to be resumed and when the
runtime PM references from the given consumer to it are dropped, it
may be suspended.  Then, the runtime-resume of the next consumer
will cause the supplier to resume again and so on.

Update the code accordingly.

Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support")
Cc: All applicable <stable@...r.kernel.org> # All applicable
---
 drivers/base/dd.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Index: linux-pm/drivers/base/dd.c
===================================================================
--- linux-pm.orig/drivers/base/dd.c
+++ linux-pm/drivers/base/dd.c
@@ -1117,6 +1117,8 @@ static void __device_release_driver(stru

 	drv = dev->driver;
 	if (drv) {
+		pm_runtime_get_sync(dev);
+
 		while (device_links_busy(dev)) {
 			__device_driver_unlock(dev, parent);

@@ -1132,8 +1134,6 @@ static void __device_release_driver(stru
 				return;
 		}

-		pm_runtime_get_sync(dev);
-
 		driver_sysfs_remove(dev);

 		if (dev->bus)