Re: [PATCH] printk deadlocks if called with runqueue lock held

[Jan Kiszka <jan.kiszka@siemens.com>]

Steven Rostedt wrote:
...
> @@ -978,7 +980,13 @@ void release_console_sem(void)
>  	console_locked = 0;
>  	up(&console_sem);

Hmm, just looking at this fragment: Doesn't up() include the risk of
running onto the runqueue lock as well?

>  	spin_unlock_irqrestore(&logbuf_lock, flags);
> -	if (wake_klogd)
> +	/*
> +	 * If we try to wake up klogd while printing with the runqueue lock
> +	 * held, this will deadlock. We don't have access to the runqueue
> +	 * lock from here, but just checking for interrupts disabled
> +	 * should be enough.
> +	 */
> +	if (!irqs_disabled() && wake_klogd)
>  		wake_up_klogd();
>  }
>  EXPORT_SYMBOL(release_console_sem);

Jan