When in the list_for_each_entry iteration, reload of p->state->settings
with a local setting from old_state will makes the list iteration in a
infinite loop.
The typical issue happened, it will frequently have printk message like:
  "not freeing pin xx (xxx) as part of deactivating group xxx - it is
already used for some other setting".
This is a compiler-dependent problem, one instance was got using Clang
version 10.0 plus arm64 architecture with linux version 4.19.

Fixes: 6e5e959dde0d ("pinctrl: API changes to support multiple states per device")
Signed-off-by: Maria Yu <quic_aiquny@quicinc.com>
Cc: stable@vger.kernel.org
---
 drivers/pinctrl/core.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c
index 1fa89be29b8f..f2977eb65522 100644
--- a/drivers/pinctrl/core.c
+++ b/drivers/pinctrl/core.c
@@ -1262,17 +1262,17 @@ 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 = p->state;
+	struct pinctrl_state *old_state = READ_ONCE(p->state);
 	int ret;
 
-	if (p->state) {
+	if (old_state) {
 		/*
 		 * For each pinmux setting in the old state, forget SW's record
 		 * of mux owner for that pingroup. Any pingroups which are
 		 * still owned by the new state will be re-acquired by the call
 		 * to pinmux_enable_setting() in the loop below.
 		 */
-		list_for_each_entry(setting, &p->state->settings, node) {
+		list_for_each_entry(setting, &old_state->settings, node) {
 			if (setting->type != PIN_MAP_TYPE_MUX_GROUP)
 				continue;
 			pinmux_disable_setting(setting);

base-commit: 9bacdd8996c77c42ca004440be610692275ff9d0
-- 
2.17.1

On Wed, Nov 15, 2023 at 11:28 AM Maria Yu <quic_aiquny@quicinc.com> wrote:

> When in the list_for_each_entry iteration, reload of p->state->settings
> with a local setting from old_state will makes the list iteration in a
> infinite loop.
> The typical issue happened, it will frequently have printk message like:
>   "not freeing pin xx (xxx) as part of deactivating group xxx - it is
> already used for some other setting".
> This is a compiler-dependent problem, one instance was got using Clang
> version 10.0 plus arm64 architecture with linux version 4.19.
>
> Fixes: 6e5e959dde0d ("pinctrl: API changes to support multiple states per device")
> Signed-off-by: Maria Yu <quic_aiquny@quicinc.com>
> Cc: stable@vger.kernel.org

Patch applied, I edited the commit message a bit.

Thanks a lot for finding this tricky bug!

Yours,
Linus Walleij