Re: [PATCH] pinctrl: core: Make p->state in order in pinctrl_commit_state

Hi Maria,

thanks for your patch!

On Thu, Oct 27, 2022 at 8:51 AM Maria Yu quic_aiquny@quicinc.com wrote:

We've got a dump that current cpu is in pinctrl_commit_state, the old_state != p->state while the stack is still in the process of pinmux_disable_setting. So it means even if the current p->state is changed in new state, the settings are not yet up-to-date enabled complete yet.

Currently p->state in different value to synchronize the pinctrl_commit_state behaviors. The p->state will have transaction like old_state -> NULL -> new_state. When in old_state, it will try to disable all the all state settings. And when after new state settings enabled, p->state will changed to the new state after that. So use smp_mb to synchronize the p->state variable and the settings in order.

---

drivers/pinctrl/core.c | 2 ++ 1 file changed, 2 insertions(+)

diff --git a/drivers/pinctrl/core.c b/drivers/pinctrl/core.c index 9e57f4c62e60..cd917a5b1a0a 100644 --- a/drivers/pinctrl/core.c +++ b/drivers/pinctrl/core.c @@ -1256,6 +1256,7 @@ static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state) } }

•   smp_mb();
    p->state = NULL;
  
    /* Apply all the settings for the new state - pinmux first */
  

@@ -1305,6 +1306,7 @@ static int pinctrl_commit_state(struct pinctrl *p, struct pinctrl_state *state) pinctrl_link_add(setting->pctldev, p->dev); }

•   smp_mb();
    p->state = state;
  
    return 0;
  

Ow!

It's not often that I loop in Paul McKenney on patches, but this is in the core of the subsystem used across all architectures so if this is a generic problem of concurrency, I really want some professional concurrency person to look at it before I apply it.

Yours, Linus Walleij