linux-kernel - [PATCH] driver core: Drop devices_kset_move_last() call from really

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Date:   Fri, 06 Jul 2018 12:00:06 +0200
From:   "Rafael J. Wysocki" <rjw@...ysocki.net>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Pingfan Liu <kernelfans@...il.com>, linux-kernel@...r.kernel.org,
        Grygorii Strashko <grygorii.strashko@...com>,
        Christoph Hellwig <hch@...radead.org>,
        Bjorn Helgaas <helgaas@...nel.org>,
        Dave Young <dyoung@...hat.com>, linux-pci@...r.kernel.org,
        Lukas Wunner <lukas@...ner.de>,
        Linux PM <linux-pm@...r.kernel.org>
Subject: [PATCH] driver core: Drop devices_kset_move_last() call from really_probe()

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

The devices_kset_move_last() call in really_probe() is a mistake
as it may cause parents to follow children in the devices_kset list
which then causes system shutdown to fail.  Namely, if a device has
children before really_probe() is called for it (which is not
uncommon), that call will cause it to be reordered after the children
in the devices_kset list and the ordering of that list will not
reflect the correct device shutdown order.

Also it causes the devices_kset list to be constantly reordered
until all drivers have been probed which is totally pointless
overhead in the majority of cases.

For that reason, revert the really_probe() modifications made by
commit 52cdbdd49853.

Fixes: 52cdbdd49853 (driver core: correct device's shutdown order)
Link: https://lore.kernel.org/lkml/CAFgQCTt7VfqM=UyCnvNFxrSw8Z6cUtAi3HUwR4_xPAc03SgHjQ@mail.gmail.com/
Reported-by: Pingfan Liu <kernelfans@...il.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 drivers/base/dd.c |    8 --------
 1 file changed, 8 deletions(-)

Index: linux-pm/drivers/base/dd.c
===================================================================
--- linux-pm.orig/drivers/base/dd.c
+++ linux-pm/drivers/base/dd.c
@@ -434,14 +434,6 @@ re_probe:
 			goto probe_failed;
 	}

-	/*
-	 * Ensure devices are listed in devices_kset in correct order
-	 * It's important to move Dev to the end of devices_kset before
-	 * calling .probe, because it could be recursive and parent Dev
-	 * should always go first
-	 */
-	devices_kset_move_last(dev);
-
 	if (dev->bus->probe) {
 		ret = dev->bus->probe(dev);
 		if (ret)