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Date:   Thu, 1 Aug 2019 17:39:36 +0200
From:   Oleg Nesterov <oleg@redhat.com>
To:     Thomas Gleixner <tglx@linutronix.de>
Cc:     LKML <linux-kernel@vger.kernel.org>, x86@kernel.org,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        Sebastian Siewior <bigeasy@linutronix.de>,
        Anna-Maria Gleixner <anna-maria@linutronix.de>,
        Steven Rostedt <rostedt@goodmis.org>,
        Julia Cartwright <julia@ni.com>,
        Paul McKenney <paulmck@linux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        John Stultz <john.stultz@linaro.org>,
        Andy Lutomirski <luto@kernel.org>,
        "Paul E. McKenney" <paulmck@linux.ibm.com>, kvm@vger.kernel.org,
        Radim Krcmar <rkrcmar@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>
Subject: Re: [patch 4/5] posix-cpu-timers: Defer timer handling to task_work
Message-ID: <20190801153936.GD31538@redhat.com>
References: <20190801143250.370326052@linutronix.de>
 <20190801143658.074833024@linutronix.de>
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On 08/01, Thomas Gleixner wrote:
>
> +static void __run_posix_cpu_timers(struct task_struct *tsk)
> +{
> +	/* FIXME: Init it proper in fork or such */
> +	init_task_work(&tsk->cpu_timer_work, posix_cpu_timers_work);
> +	task_work_add(tsk, &tsk->cpu_timer_work, true);
> +}

What if update_process_times/run_posix_cpu_timers is called again before
this task does task_work_run() ?

somehow it should check that ->cpu_timer_work is not already queued...

Or suppose that this is called when task_work_run() executes this
cpu_timer_work. Looks like you need another flag checked by
__run_posix_cpu_timers() and cleare in posix_cpu_timers_work() ?

Oleg.