linux-kernel - Re: [PATCH RT 5/8] sched: Fix affine_move

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Date:   Sun, 25 Jul 2021 07:03:49 +0200
From:   Pavel Machek <pavel@....cz>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     linux-kernel@...r.kernel.org,
        linux-rt-users <linux-rt-users@...r.kernel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        John Kacur <jkacur@...hat.com>, Daniel Wagner <wagi@...om.org>,
        Tom Zanussi <zanussi@...nel.org>,
        "Srivatsa S. Bhat" <srivatsa@...il.mit.edu>, stable@...nel.org,
        "Peter Zijlstra (Intel)" <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: Re: [PATCH RT 5/8] sched: Fix affine_move_task() self-concurrency

Hi!

> 5.10.47-rt46-rc1 stable review patch.
> If anyone has any objections, please let me know.
> 
> Add set_affinity_pending::stop_pending, to indicate if a stopper is in
> progress.
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 9cbe12d8c5bd..20588a59300d 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1900,6 +1900,7 @@ struct migration_arg {
>  
>  struct set_affinity_pending {
>  	refcount_t		refs;
> +	unsigned int		stop_pending;
>  	struct completion	done;
>  	struct cpu_stop_work	stop_work;
>  	struct migration_arg	arg;

For better readability, this should be bool, AFAICT.

>  		 * and have the stopper function handle it all race-free.
>  		 */
> +		stop_pending = pending->stop_pending;
> +		if (!stop_pending)
> +			pending->stop_pending = true;
>  
...because it is used as bool.

									Pavel

-- 
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