linux-kernel - [PATCH v1] driver core: Fix handling of SYNC_STATE

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Date:   Tue, 19 May 2020 21:36:26 -0700
From:   Saravana Kannan <saravanak@...gle.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Saravana Kannan <saravanak@...gle.com>
Cc:     kernel-team@...roid.com,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1] driver core: Fix handling of SYNC_STATE_ONLY + STATELESS
 device links

Commit 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link
implementation") didn't completely fix STATELESS + SYNC_STATE_ONLY
handling.

What looks like an optimization in that commit is actually a bug that
causes an if condition to always take the else path. This prevents
reordering of devices in the dpm_list when a DL_FLAG_STATELESS device
link is create on top of an existing DL_FLAG_SYNC_STATE_ONLY device
link.

Fixes: 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link implementation")
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
---
Sigh... device links are tricky and hard! Sorry about the endless fixes :(
Also, how was this not caught by the compiler as a warning?

-Saravana

 drivers/base/core.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 83a3e0b62ce3..dfd4e94ef790 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -543,12 +543,14 @@ struct device_link *device_link_add(struct device *consumer,
 
 		if (flags & DL_FLAG_STATELESS) {
 			kref_get(&link->kref);
-			link->flags |= DL_FLAG_STATELESS;
 			if (link->flags & DL_FLAG_SYNC_STATE_ONLY &&
-			    !(link->flags & DL_FLAG_STATELESS))
+			    !(link->flags & DL_FLAG_STATELESS)) {
+				link->flags |= DL_FLAG_STATELESS;
 				goto reorder;
-			else
+			} else {
+				link->flags |= DL_FLAG_STATELESS;
 				goto out;
+			}
 		}
 
 		/*
-- 
2.26.2.761.g0e0b3e54be-goog