linux-kernel - Re: [patch V2 06/10] timer: Restructure internal locking

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Date:   Wed, 19 Apr 2017 09:07:04 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        John Stultz <john.stultz@...aro.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Anna-Maria Gleixner <anna-maria@...utronix.de>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        linux-pm@...r.kernel.org, Arjan van de Ven <arjan@...radead.org>,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Rik van Riel <riel@...hat.com>,
        Richard Cochran <rcochran@...utronix.de>
Subject: Re: [patch V2 06/10] timer: Restructure internal locking

On Tue, Apr 18, 2017 at 01:11:08PM +0200, Thomas Gleixner wrote:

> +++ b/kernel/time/timer.c
> @@ -1651,17 +1651,14 @@ void update_process_times(int user_tick)
>  /**
>   * __run_timers - run all expired timers (if any) on this CPU.
>   * @base: the timer vector to be processed.
> + *
> + * Caller must hold the base lock.
>   */
>  static inline void __run_timers(struct timer_base *base)
>  {
>  	struct hlist_head heads[LVL_DEPTH];
>  	int levels;
>  
> -	if (!time_after_eq(jiffies, base->clk))
> -		return;
> -
> -	spin_lock_irq(&base->lock);
> -

	lockdep_assert_held(&base->lock);


Is so ever much more useful than a comment.

>  	while (time_after_eq(jiffies, base->clk)) {
>  
>  		levels = collect_expired_timers(base, heads);