linux-kernel - Re: [PATCH] posix-timers: Release the acquired lock before returning

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Date:   Mon, 26 Jun 2023 16:19:50 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     You Kangren <youkangren@...o.com>,
        "open list:POSIX CLOCKS and TIMERS" <linux-kernel@...r.kernel.org>
Cc:     opensource.kernel@...o.com, youkangren@...o.com
Subject: Re: [PATCH] posix-timers: Release the acquired lock before returning

On Mon, Jun 26 2023 at 20:00, You Kangren wrote:
> Release the acquired lock before returning to prevent errors

Seriously?

> @@ -599,6 +599,7 @@ static struct k_itimer *__lock_timer(timer_t timer_id, unsigned long *flags)
>  		 */
>  		if (timr->it_signal == current->signal) {
>  			rcu_read_unlock();
> +			spin_unlock_irqrestore(&timr->it_lock, *flags);
>  			return timr;

The name of this function is __lock_timer() so it better returns with
the timer locked, no?

>  		}
>  		spin_unlock_irqrestore(&timr->it_lock, *flags);
> @@ -1066,9 +1067,10 @@ static void itimer_delete(struct k_itimer *timer)
>  		 * do_exit() only for the last thread of the thread group.
>  		 * So no other task can access and delete that timer.
>  		 */
> -		if (WARN_ON_ONCE(timer_wait_running(timer, &flags) != timer))
> +		if (WARN_ON_ONCE(timer_wait_running(timer, &flags) != timer)) {
> +			spin_unlock_irqrestore(&timer->it_lock, flags);

There is no lock held in that case.

Thanks,

        tglx