linux-kernel - Re: [PATCH 1/4] sched/wakeup: Strengthen current_save_and_set_rtlock_wait

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Message-ID: <20210910124530.iezmxpzzhkbl6gwt@linutronix.de>
Date:   Fri, 10 Sep 2021 14:45:30 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     tglx@...utronix.de, boqun.feng@...il.com,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Davidlohr Bueso <dave@...olabs.net>,
        Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Mike Galbraith <efault@....de>,
        Daniel Bristot de Oliveira <bristot@...hat.com>
Subject: Re: [PATCH 1/4] sched/wakeup: Strengthen
 current_save_and_set_rtlock_wait_state()

On 2021-09-09 12:59:16 [+0200], Peter Zijlstra wrote:
> --- a/include/linux/sched.h
> +++ b/include/linux/sched.h
> @@ -253,22 +254,24 @@ struct task_group;
>   */
>  #define current_save_and_set_rtlock_wait_state()			\
>  	do {								\
> -		lockdep_assert_irqs_disabled();				\
> -		raw_spin_lock(&current->pi_lock);			\
> +		unsigned long flags; /* may shadow */			\
could we haz __flags so no shadow?

> +									\
> +		raw_spin_lock_irqsave(&current->pi_lock, flags);	\
>  		current->saved_state = current->__state;		\
>  		debug_rtlock_wait_set_state();				\
> -		WRITE_ONCE(current->__state, TASK_RTLOCK_WAIT);		\
> -		raw_spin_unlock(&current->pi_lock);			\
> +		smp_store_mb(current->__state, TASK_RTLOCK_WAIT);	\
> +		raw_spin_unlock_irqrestore(&current->pi_lock, flags);	\

Sebastian