Re: FAILED: patch "[PATCH] driver core: Extend device_is_dependent()" failed to apply to 4.14-stable tree

[Sudip Mukherjee <sudipm.mukherjee@gmail.com>]

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Hi Greg,

On Mon, Jan 25, 2021 at 03:22:49PM +0100, gregkh@linuxfoundation.org wrote:
> 
> The patch below does not apply to the 4.14-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.

Here is the backport along with:
e16f4f3e0b7d ("base: core: Remove WARN_ON from link dependencies check") for
easy backporting.

--
Regards
Sudip

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From f39c5cb27e89fbfc98d744ba57f50c09928e5b95 Mon Sep 17 00:00:00 2001
From: Benjamin Gaignard <benjamin.gaignard@linaro.org>
Date: Mon, 16 Jul 2018 13:37:44 +0200
Subject: [PATCH 1/2] base: core: Remove WARN_ON from link dependencies check

commit e16f4f3e0b7daecd48d4f944ab4147c1a6cb16a8 upstream

In some cases the link between between customer and supplier
already exist, for example when a device use its parent as a supplier.
Do not warn about already existing dependencies because device_link_add()
takes care of this case.

Link: http://lkml.kernel.org/r/20180709111753eucas1p1f32e66fb2f7ea3216097cd72a132355d~-rzycA5Rg0378203782eucas1p1C@eucas1p1.samsung.com

Reported-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Benjamin Gaignard <benjamin.gaignard@st.com>
Reviewed-by: Rafael J. Wysocki <rafael@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/base/core.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index a11652d77c7f..95641d34ea1b 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -109,7 +109,7 @@ static int device_is_dependent(struct device *dev, void *target)
 	struct device_link *link;
 	int ret;
 
-	if (WARN_ON(dev == target))
+	if (dev == target)
 		return 1;
 
 	ret = device_for_each_child(dev, target, device_is_dependent);
@@ -117,7 +117,7 @@ static int device_is_dependent(struct device *dev, void *target)
 		return ret;
 
 	list_for_each_entry(link, &dev->links.consumers, s_node) {
-		if (WARN_ON(link->consumer == target))
+		if (link->consumer == target)
 			return 1;
 
 		ret = device_is_dependent(link->consumer, target);
-- 
2.29.2


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From 65e765891ad85eca6a5817d1966432a72c261d82 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Date: Fri, 15 Jan 2021 19:30:51 +0100
Subject: [PATCH 2/2] driver core: Extend device_is_dependent()

commit 3d1cf435e201d1fd63e4346b141881aed086effd upstream

If the device passed as the target (second argument) to
device_is_dependent() is not completely registered (that is, it has
been initialized, but not added yet), but the parent pointer of it
is set, it may be missing from the list of the parent's children
and device_for_each_child() called by device_is_dependent() cannot
be relied on to catch that dependency.

For this reason, modify device_is_dependent() to check the ancestors
of the target device by following its parent pointer in addition to
the device_for_each_child() walk.

Fixes: 9ed9895370ae ("driver core: Functional dependencies tracking support")
Reported-by: Stephan Gerhold <stephan@gerhold.net>
Tested-by: Stephan Gerhold <stephan@gerhold.net>
Reviewed-by: Saravana Kannan <saravanak@google.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/17705994.d592GUb2YH@kreacher
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sudip Mukherjee <sudipm.mukherjee@gmail.com>
---
 drivers/base/core.c | 17 ++++++++++++++++-
 1 file changed, 16 insertions(+), 1 deletion(-)

diff --git a/drivers/base/core.c b/drivers/base/core.c
index 95641d34ea1b..92415a748ad2 100644
--- a/drivers/base/core.c
+++ b/drivers/base/core.c
@@ -96,6 +96,16 @@ void device_links_read_unlock(int not_used)
 }
 #endif /* !CONFIG_SRCU */
 
+static bool device_is_ancestor(struct device *dev, struct device *target)
+{
+	while (target->parent) {
+		target = target->parent;
+		if (dev == target)
+			return true;
+	}
+	return false;
+}
+
 /**
  * device_is_dependent - Check if one device depends on another one
  * @dev: Device to check dependencies for.
@@ -109,7 +119,12 @@ static int device_is_dependent(struct device *dev, void *target)
 	struct device_link *link;
 	int ret;
 
-	if (dev == target)
+	/*
+	 * The "ancestors" check is needed to catch the case when the target
+	 * device has not been completely initialized yet and it is still
+	 * missing from the list of children of its parent device.
+	 */
+	if (dev == target || device_is_ancestor(dev, target))
 		return 1;
 
 	ret = device_for_each_child(dev, target, device_is_dependent);
-- 
2.29.2