linux-kernel - [PATCH 5.6 028/161] driver core: Update device link status correctly for SYNC_STATE

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Date:   Tue, 16 Jun 2020 17:33:38 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Michael Walle <michael@...le.cc>,
        Saravana Kannan <saravanak@...gle.com>,
        "Rafael J. Wysocki" <rrafael.j.wysocki@...el.com>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH 5.6 028/161] driver core: Update device link status correctly for SYNC_STATE_ONLY links

From: Saravana Kannan <saravanak@...gle.com>

[ Upstream commit 8c3e315d4296421cd26b3300ee0ac117f0877f20 ]

When SYNC_STATE_ONLY support was added in commit 05ef983e0d65 ("driver
core: Add device link support for SYNC_STATE_ONLY flag"),
SYNC_STATE_ONLY links were treated similar to STATELESS links in terms
of not blocking consumer probe if the supplier hasn't probed yet.

That caused a SYNC_STATE_ONLY device link's status to not get updated.
Since SYNC_STATE_ONLY device link is no longer useful once the
consumer probes, commit 21c27f06587d ("driver core: Fix
SYNC_STATE_ONLY device link implementation") addresses the status
update issue by deleting the SYNC_STATE_ONLY device link instead of
complicating the status update code.

However, there are still some cases where we need to update the status
of a SYNC_STATE_ONLY device link. This is because a SYNC_STATE_ONLY
device link can later get converted into a normal MANAGED device link
when a normal MANAGED device link is created between a supplier and
consumer that already have a SYNC_STATE_ONLY device link between them.

If a SYNC_STATE_ONLY device link's status isn't maintained correctly
till it's converted to a normal MANAGED device link, then the normal
MANAGED device link will end up with a wrong link status. This can cause
a warning stack trace[1] when the consumer device probes successfully.

This commit fixes the SYNC_STATE_ONLY device link status update issue
where it wouldn't transition correctly from DL_STATE_DORMANT or
DL_STATE_AVAILABLE to DL_STATE_CONSUMER_PROBE. It also resets the status
back to DL_STATE_DORMANT or DL_STATE_AVAILABLE if the consumer probe
fails.

[1] - https://lore.kernel.org/lkml/20200522204120.3b3c9ed6@apollo/
Fixes: 05ef983e0d65 ("driver core: Add device link support for SYNC_STATE_ONLY flag")
Fixes: 21c27f06587d ("driver core: Fix SYNC_STATE_ONLY device link implementation")
Reported-by: Michael Walle <michael@...le.cc>
Tested-by: Michael Walle <michael@...le.cc>
Signed-off-by: Saravana Kannan <saravanak@...gle.com>
Reviewed-by: Rafael J. Wysocki <rrafael.j.wysocki@...el.com>
Link: https://lore.kernel.org/r/20200526220928.49939-1-saravanak@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 drivers/base/core.c | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 68277687c160..3c4ecb824247 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -643,9 +643,17 @@ static void device_links_missing_supplier(struct device *dev)
 {
 	struct device_link *link;

-	list_for_each_entry(link, &dev->links.suppliers, c_node)
-		if (link->status == DL_STATE_CONSUMER_PROBE)
+	list_for_each_entry(link, &dev->links.suppliers, c_node) {
+		if (link->status != DL_STATE_CONSUMER_PROBE)
+			continue;
+
+		if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
 			WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
+		} else {
+			WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
+			WRITE_ONCE(link->status, DL_STATE_DORMANT);
+		}
+	}
 }

 /**
@@ -684,11 +692,11 @@ int device_links_check_suppliers(struct device *dev)
 	device_links_write_lock();

 	list_for_each_entry(link, &dev->links.suppliers, c_node) {
-		if (!(link->flags & DL_FLAG_MANAGED) ||
-		    link->flags & DL_FLAG_SYNC_STATE_ONLY)
+		if (!(link->flags & DL_FLAG_MANAGED))
 			continue;

-		if (link->status != DL_STATE_AVAILABLE) {
+		if (link->status != DL_STATE_AVAILABLE &&
+		    !(link->flags & DL_FLAG_SYNC_STATE_ONLY)) {
 			device_links_missing_supplier(dev);
 			ret = -EPROBE_DEFER;
 			break;
@@ -949,11 +957,21 @@ static void __device_links_no_driver(struct device *dev)
 		if (!(link->flags & DL_FLAG_MANAGED))
 			continue;

-		if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER)
+		if (link->flags & DL_FLAG_AUTOREMOVE_CONSUMER) {
 			device_link_drop_managed(link);
-		else if (link->status == DL_STATE_CONSUMER_PROBE ||
-			 link->status == DL_STATE_ACTIVE)
+			continue;
+		}
+
+		if (link->status != DL_STATE_CONSUMER_PROBE &&
+		    link->status != DL_STATE_ACTIVE)
+			continue;
+
+		if (link->supplier->links.status == DL_DEV_DRIVER_BOUND) {
 			WRITE_ONCE(link->status, DL_STATE_AVAILABLE);
+		} else {
+			WARN_ON(!(link->flags & DL_FLAG_SYNC_STATE_ONLY));
+			WRITE_ONCE(link->status, DL_STATE_DORMANT);
+		}
 	}

 	dev->links.status = DL_DEV_NO_DRIVER;
-- 
2.25.1