Re: [bug report] gpio: remove gpio_lock

[Bartosz Golaszewski <brgl@xxxxxxxx>]

On Wed, Feb 14, 2024 at 8:31 AM Dan Carpenter <dan.carpenter@xxxxxxxxxx> wrote:
>
> Hello Bartosz Golaszewski,
>
> The patch 35b545332b80: "gpio: remove gpio_lock" from Jan 12, 2024
> (linux-next), leads to the following Smatch static checker warning:
>
>         drivers/gpio/gpiolib.c:120 desc_set_label()
>         warn: sleeping in atomic context
>
> drivers/gpio/gpiolib.c
>     115 static int desc_set_label(struct gpio_desc *desc, const char *label)
>     116 {
>     117         const char *new = NULL, *old;
>     118
>     119         if (label) {
> --> 120                 new = kstrdup_const(label, GFP_KERNEL);
>                                                    ^^^^^^^^^^
> This used to be GFP_ATOMIC
>

This not being GFP_ATOMIC is the least of the problems, we could
simply change it back...

>     121                 if (!new)
>     122                         return -ENOMEM;
>     123         }
>     124
>     125         old = rcu_replace_pointer(desc->label, new, 1);
>     126         synchronize_srcu(&desc->srcu);

... but this synchronize_srcu() call will trigger the same issue.

>     127         kfree_const(old);
>     128
>     129         return 0;
>     130 }
>
> The call tree that triggers the warning is:
>
> asc_set_termios() <- disables preempt
> -> gpiod_set_consumer_name()
>    -> desc_set_label()
>
> asc_set_termios() is holding uart_port_lock_irqsave(port, &flags);
>

So it should not be calling gpiod_set_consumer_name() but well, technical dept.

I'll see if this can be changed.

Bart

> regards,
> dan carpenter
>