linux-kernel - Re: [PATCH] posix-cpu-timers: Implement the missing timer_wait

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Date:   Wed, 19 Apr 2023 09:33:20 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Frederic Weisbecker <frederic@...nel.org>
Cc:     Marco Elver <elver@...gle.com>,
        syzbot <syzbot+3b14b2ed9b3d06dcaa07@...kaller.appspotmail.com>,
        linux-kernel@...r.kernel.org, syzkaller-bugs@...glegroups.com,
        Anna-Maria Behnsen <anna-maria@...utronix.de>,
        Jacob Keller <jacob.e.keller@...el.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] posix-cpu-timers: Implement the missing
 timer_wait_running callback

On Tue, Apr 18 2023 at 18:44, Frederic Weisbecker wrote:
> Le Mon, Apr 17, 2023 at 03:37:55PM +0200, Thomas Gleixner a écrit :
>>  struct cpu_timer {
>>  	struct timerqueue_node	node;
>> @@ -72,6 +74,7 @@ struct cpu_timer {
>>  	struct pid		*pid;
>>  	struct list_head	elist;
>>  	int			firing;
>> +	struct task_struct	*handling;
>
> I guess it can be made __rcu

Indeed. 
>>  		if (likely(cpu_firing >= 0))
>>  			cpu_timer_fire(timer);
>> +		/* See posix_cpu_timer_wait_running() */
>> +		WRITE_ONCE(timer->it.cpu.handling, NULL);
>
> And rcu_assign_pointer()

I fix that up on the fly.

> Aside the boring details:
>
> Reviewed-by: Frederic Weisbecker <frederic@...nel.org>

Thanks for going through this!