[3.16.y-ckt stable] Patch "pinctrl: Don't just pretend to protect pinctrl_maps, do it for real" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    pinctrl: Don't just pretend to protect pinctrl_maps, do it for real

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt12.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From ab3bd64bdd36cd4830e109503268b625d8ce0e66 Mon Sep 17 00:00:00 2001
From: Doug Anderson <dianders at chromium.org>
Date: Fri, 1 May 2015 09:01:27 -0700
Subject: pinctrl: Don't just pretend to protect pinctrl_maps, do it for real

commit c5272a28566b00cce79127ad382406e0a8650690 upstream.

Way back, when the world was a simpler place and there was no war, no
evil, and no kernel bugs, there was just a single pinctrl lock.  That
was how the world was when (57291ce pinctrl: core device tree mapping
table parsing support) was written.  In that case, there were
instances where the pinctrl mutex was already held when
pinctrl_register_map() was called, hence a "locked" parameter was
passed to the function to indicate that the mutex was already locked
(so we shouldn't lock it again).

A few years ago in (42fed7b pinctrl: move subsystem mutex to
pinctrl_dev struct), we switched to a separate pinctrl_maps_mutex.
...but (oops) we forgot to re-think about the whole "locked" parameter
for pinctrl_register_map().  Basically the "locked" parameter appears
to still refer to whether the bigger pinctrl_dev mutex is locked, but
we're using it to skip locks of our (now separate) pinctrl_maps_mutex.

That's kind of a bad thing(TM).  Probably nobody noticed because most
of the calls to pinctrl_register_map happen at boot time and we've got
synchronous device probing.  ...and even cases where we're
asynchronous don't end up actually hitting the race too often.  ...but
after banging my head against the wall for a bug that reproduced 1 out
of 1000 reboots and lots of looking through kgdb, I finally noticed
this.

Anyway, we can now safely remove the "locked" parameter and go back to
a war-free, evil-free, and kernel-bug-free world.

Fixes: 42fed7ba44e4 ("pinctrl: move subsystem mutex to pinctrl_dev struct")
Signed-off-by: Doug Anderson <dianders at chromium.org>
Signed-off-by: Linus Walleij <linus.walleij at linaro.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/pinctrl/core.c       | 10 ++++------
 drivers/pinctrl/core.h       |  2 +-
 drivers/pinctrl/devicetree.c |  2 +-
 3 files changed, 6 insertions(+), 8 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 81ca0ce4c909..84f946a7a405 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1124,7 +1124,7 @@ void devm_pinctrl_put(struct pinctrl *p)
 EXPORT_SYMBOL_GPL(devm_pinctrl_put);

 int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps,
-			 bool dup, bool locked)
+			 bool dup)
 {
 	int i, ret;
 	struct pinctrl_maps *maps_node;
@@ -1192,11 +1192,9 @@ int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps,
 		maps_node->maps = maps;
 	}

-	if (!locked)
-		mutex_lock(&pinctrl_maps_mutex);
+	mutex_lock(&pinctrl_maps_mutex);
 	list_add_tail(&maps_node->node, &pinctrl_maps);
-	if (!locked)
-		mutex_unlock(&pinctrl_maps_mutex);
+	mutex_unlock(&pinctrl_maps_mutex);

 	return 0;
 }
@@ -1211,7 +1209,7 @@ int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps,
 int pinctrl_register_mappings(struct pinctrl_map const *maps,
 			      unsigned num_maps)
 {
-	return pinctrl_register_map(maps, num_maps, true, false);
+	return pinctrl_register_map(maps, num_maps, true);
 }

 void pinctrl_unregister_map(struct pinctrl_map const *map)
diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index 75476b3d87da..b24ea846c867 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -183,7 +183,7 @@ static inline struct pin_desc *pin_desc_get(struct pinctrl_dev *pctldev,
 }

 int pinctrl_register_map(struct pinctrl_map const *maps, unsigned num_maps,
-			 bool dup, bool locked);
+			 bool dup);
 void pinctrl_unregister_map(struct pinctrl_map const *map);

 extern int pinctrl_force_sleep(struct pinctrl_dev *pctldev);
diff --git a/drivers/pinctrl/devicetree.c b/drivers/pinctrl/devicetree.c
index eda13de2e7c0..0bbf7d71b281 100644
--- a/drivers/pinctrl/devicetree.c
+++ b/drivers/pinctrl/devicetree.c
@@ -92,7 +92,7 @@ static int dt_remember_or_free_map(struct pinctrl *p, const char *statename,
 	dt_map->num_maps = num_maps;
 	list_add_tail(&dt_map->node, &p->dt_maps);

-	return pinctrl_register_map(map, num_maps, false, true);
+	return pinctrl_register_map(map, num_maps, false);
 }

 struct pinctrl_dev *of_pinctrl_get(struct device_node *np)