Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Valentin Schneider <vschneid@redhat.com>
To:     Schspa Shi <schspa@gmail.com>, mingo@redhat.com,
        peterz@infradead.org, juri.lelli@redhat.com,
        vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
        rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
        bristot@redhat.com
Cc:     linux-kernel@vger.kernel.org, zhaohui.shi@horizon.ai,
        Schspa Shi <schspa@gmail.com>
Subject: Re: [PATCH] sched: fix bad task migration for rt tasks
In-Reply-To: <20220623182932.58589-1-schspa@gmail.com>
References: <20220623182932.58589-1-schspa@gmail.com>
Date:   Fri, 24 Jun 2022 11:56:38 +0100
Message-ID: <xhsmhv8sq5nyx.mognet@vschneid.remote.csb>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On 24/06/22 02:29, Schspa Shi wrote:
> @@ -1998,12 +1998,15 @@ static struct rq *find_lock_lowest_rq(struct task_struct *task, struct rq *rq)
>  			 * the mean time, task could have
>  			 * migrated already or had its affinity changed.
>  			 * Also make sure that it wasn't scheduled on its rq.
> +			 * It is possible the task has running for a while,
> +			 * And we check task migration disable flag again.
>  			 */
>  			if (unlikely(task_rq(task) != rq ||
>  				     !cpumask_test_cpu(lowest_rq->cpu, &task->cpus_mask) ||

cf. 95158a89dd50 ("sched,rt: Use the full cpumask for balancing"), this
made sense to me back then but not so much anymore... Shouldn't this have
remained a ->cpus_ptr check?

I'm going to revisit that commit, I evicted too much of it.

>  				     task_running(rq, task) ||
>  				     !rt_task(task) ||
> -				     !task_on_rq_queued(task))) {
> +				     !task_on_rq_queued(task) ||
> +				     is_migration_disabled(task))) {
>  
>  				double_unlock_balance(rq, lowest_rq);
>  				lowest_rq = NULL;
> -- 
> 2.24.3 (Apple Git-128)