linux-kernel - Re: Workqueues splat due to ending up on wrong CPU

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Message-ID: <20191203100659.GA2871@hirez.programming.kicks-ass.net>
Date:   Tue, 3 Dec 2019 11:06:59 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Tejun Heo <tj@...nel.org>
Cc:     "Paul E. McKenney" <paulmck@...nel.org>, jiangshanlai@...il.com,
        linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: Workqueues splat due to ending up on wrong CPU

On Tue, Dec 03, 2019 at 10:55:21AM +0100, Peter Zijlstra wrote:
> @@ -1100,6 +1099,12 @@ void cpuhp_online_idle(enum cpuhp_state state)
>  	if (state != CPUHP_AP_ONLINE_IDLE)
>  		return;
>  
> +	/*
> +	 * Unpark the stopper thread before we start the idle thread; this

s/thread/loop/, _this_ is the idle thread :-)

> +	 * ensures the stopper is always available.
> +	 */
> +	stop_machine_unpark(smp_processor_id());
> +
>  	st->state = CPUHP_AP_ONLINE_IDLE;
>  	complete_ap_thread(st, true);
>  }