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Message-ID: <20150604105537.GT18673@twins.programming.kicks-ass.net>
Date: Thu, 4 Jun 2015 12:55:37 +0200
From: Peter Zijlstra <peterz@...radead.org>
To: Kirill Tkhai <tkhai@...dex.ru>
Cc: "umgwanakikbuti@...il.com" <umgwanakikbuti@...il.com>,
"mingo@...e.hu" <mingo@...e.hu>,
"ktkhai@...allels.com" <ktkhai@...allels.com>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"juri.lelli@...il.com" <juri.lelli@...il.com>,
"pang.xunlei@...aro.org" <pang.xunlei@...aro.org>,
"oleg@...hat.com" <oleg@...hat.com>,
"wanpeng.li@...ux.intel.com" <wanpeng.li@...ux.intel.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 8/9] hrtimer: Allow hrtimer::function() to free the timer
On Thu, Jun 04, 2015 at 12:49:02PM +0200, Peter Zijlstra wrote:
> Needs more comments at the very least, its fully of trickery.
>
> @@ -1118,10 +1125,16 @@ static void __run_hrtimer(struct hrtimer
> enum hrtimer_restart (*fn)(struct hrtimer *);
> int restart;
>
> - WARN_ON(!irqs_disabled());
> + lockdep_assert_held(&cpu_base->lock);
>
> debug_deactivate(timer);
> - base->running = timer;
> + cpu_base->running = timer;
> +
> + /*
> + * separate the ->running assignment from the ->state assignment
> + */
> + write_seqcount_begin(&cpu_base->seq);
Maybe these need to be raw_write_seqcount_latch()..
> +
> __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE, 0);
> timer_stats_account_hrtimer(timer);
> fn = timer->function;
> @@ -1150,8 +1163,13 @@ static void __run_hrtimer(struct hrtimer
> !(timer->state & HRTIMER_STATE_ENQUEUED))
> enqueue_hrtimer(timer, base);
>
> - WARN_ON_ONCE(base->running != timer);
> - base->running = NULL;
> + /*
> + * separate the ->running assignment from the ->state assignment
> + */
> + write_seqcount_end(&cpu_base->seq);
> +
> + WARN_ON_ONCE(cpu_base->running != timer);
> + cpu_base->running = NULL;
> }
>
> static void __hrtimer_run_queues(struct hrtimer_cpu_base *cpu_base, ktime_t now)
--
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