[PATCH v2] pinctrl: Add lock to ensure the state atomization

[Maria Yu <quic_aiquny@xxxxxxxxxxx>]

Currently pinctrl_select_state is an export symbol and don't have
effective re-entrance protect design. During async probing of devices
it's possible to end up in pinctrl_select_state() from multiple
contexts simultaneously, so make it thread safe.
More over, when the real racy happened, the system frequently have
printk message like:
  "not freeing pin xx (xxx) as part of deactivating group xxx - it is
already used for some other setting".
Finally the system crashed after the flood log.
Add per pinctrl lock to ensure the old state and new state transition
atomization.
Also move dev error print message outside the region with interrupts
disabled.

Fixes: 4198a9b57106 ("pinctrl: avoid reload of p state in list iteration")
Signed-off-by: Maria Yu <quic_aiquny@xxxxxxxxxxx>
---
 drivers/pinctrl/core.c | 11 +++++++++--
 drivers/pinctrl/core.h |  2 ++
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index f2977eb65522..a19c286bf82e 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1066,6 +1066,7 @@ static struct pinctrl *create_pinctrl(struct device *dev,
 	p->dev = dev;
 	INIT_LIST_HEAD(&p->states);
 	INIT_LIST_HEAD(&p->dt_maps);
+	spin_lock_init(&p->lock);
 
 	ret = pinctrl_dt_to_map(p, pctldev);
 	if (ret < 0) {
@@ -1262,9 +1263,12 @@ static void pinctrl_link_add(struct pinctrl_dev *pctldev,
 static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state)
 {
 	struct pinctrl_setting *setting, *setting2;
-	struct pinctrl_state *old_state = READ_ONCE(p->state);
+	struct pinctrl_state *old_state;
 	int ret;
+	unsigned long flags;
 
+	spin_lock_irqsave(&p->lock, flags);
+	old_state = p->state;
 	if (old_state) {
 		/*
 		 * For each pinmux setting in the old state, forget SW's record
@@ -1329,11 +1333,11 @@ static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state)
 	}
 
 	p->state = state;
+	spin_unlock_irqrestore(&p->lock, flags);
 
 	return 0;
 
 unapply_new_state:
-	dev_err(p->dev, "Error applying setting, reverse things back\n");
 
 	list_for_each_entry(setting2, &state->settings, node) {
 		if (&setting2->node == &setting->node)
@@ -1349,6 +1353,9 @@ static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state)
 			pinmux_disable_setting(setting2);
 	}
 
+	spin_unlock_irqrestore(&p->lock, flags);
+
+	dev_err(p->dev, "Error applying setting, reverse things back\n");
 	/* There's no infinite recursive loop here because p->state is NULL */
 	if (old_state)
 		pinctrl_select_state(p, old_state);
diff --git a/drivers/pinctrl/core.h b/drivers/pinctrl/core.h
index 530370443c19..86fc41393f7b 100644
--- a/drivers/pinctrl/core.h
+++ b/drivers/pinctrl/core.h
@@ -12,6 +12,7 @@
 #include <linux/list.h>
 #include <linux/mutex.h>
 #include <linux/radix-tree.h>
+#include <linux/spinlock.h>
 #include <linux/types.h>
 
 #include <linux/pinctrl/machine.h>
@@ -91,6 +92,7 @@ struct pinctrl {
 	struct pinctrl_state *state;
 	struct list_head dt_maps;
 	struct kref users;
+	spinlock_t lock;
 };
 
 /**

base-commit: 26aff849438cebcd05f1a647390c4aa700d5c0f1
-- 
2.17.1