linux-kernel - [PATCH] PM: sleep: core: Drop racy and redundant checks from device

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Date:   Sun, 29 Mar 2020 16:11:18 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Linux PM <linux-pm@...r.kernel.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Alan Stern <stern@...land.harvard.edu>
Subject: [PATCH] PM: sleep: core: Drop racy and redundant checks from device_prepare()

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

Alan Stern points out that the WARN_ON() check in device_prepare()
is racy (because the PM-runtime API can be disabled briefly for any
device at any time and system suspend can start at any time too) and
the pm_runtime_suspended() check in the computation of the
direct_complete flag value is redundant (because it will be
repeated later anyway).

Drop both these checks accordingly.

Reported-by: Alan Stern <stern@...land.harvard.edu>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/base/power/main.c |    7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

Index: linux-pm/drivers/base/power/main.c
===================================================================
--- linux-pm.orig/drivers/base/power/main.c
+++ linux-pm/drivers/base/power/main.c
@@ -1922,10 +1922,6 @@ static int device_prepare(struct device
 	if (dev->power.syscore)
 		return 0;
 
-	WARN_ON(!pm_runtime_enabled(dev) &&
-		dev_pm_test_driver_flags(dev, DPM_FLAG_SMART_SUSPEND |
-					      DPM_FLAG_LEAVE_SUSPENDED));
-
 	/*
 	 * If a device's parent goes into runtime suspend at the wrong time,
 	 * it won't be possible to resume the device.  To prevent this we
@@ -1973,8 +1969,7 @@ unlock:
 	 */
 	spin_lock_irq(&dev->power.lock);
 	dev->power.direct_complete = state.event == PM_EVENT_SUSPEND &&
-		((pm_runtime_suspended(dev) && ret > 0) ||
-		 dev->power.no_pm_callbacks) &&
+		(ret > 0 || dev->power.no_pm_callbacks) &&
 		!dev_pm_test_driver_flags(dev, DPM_FLAG_NEVER_SKIP);
 	spin_unlock_irq(&dev->power.lock);
 	return 0;