linux-kernel - Re: [PATCH v4 14/15] Remove the ext server BW before changing tasks to FAIR

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <33a80bba-22b7-4c2e-9acb-14d590dad55f@nvidia.com>
Date: Wed, 18 Jun 2025 09:21:07 -0400
From: Joel Fernandes <joelagnelf@...dia.com>
To: Andrea Righi <arighi@...dia.com>
Cc: linux-kernel@...r.kernel.org, Tejun Heo <tj@...nel.org>,
 David Vernet <void@...ifault.com>, Changwoo Min <changwoo@...lia.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>
Subject: Re: [PATCH v4 14/15] Remove the ext server BW before changing tasks
 to FAIR



On 6/17/2025 4:42 PM, Andrea Righi wrote:
>> +
>> +		/*
>> +		 * We are unloading the sched_ext scheduler, we do not need its
>> +		 * DL server bandwidth anymore, remove it for all CPUs. Whenever
>> +		 * the first SCX task is enqueued (when scx is re-loaded), its DL
>> +		 * server bandwidth will be re-initialized.
>> +		 */
>> +		rq_lock_irqsave(rq, &rf);
>> +		update_rq_clock(rq);
>> +		if (dl_server_active(&rq->ext_server))
>> +			dl_server_stop(&rq->ext_server);
>> +		dl_server_remove_params(&rq->ext_server);
>> +		rq_unlock_irqrestore(rq, &rf);
>> +	}
>> +
>> +
>>  	scx_task_iter_start(&sti);
>>  	while ((p = scx_task_iter_next_locked(&sti))) {
>>  		const struct sched_class *old_class = p->sched_class;
>> @@ -4985,26 +5010,12 @@ static void scx_disable_workfn(struct kthread_work *work)
>>  
>>  	for_each_possible_cpu(cpu) {
>>  		struct rq *rq = cpu_rq(cpu);
>> -		struct rq_flags rf;
>>  
>>  		/*
>>  		 * Invalidate all the rq clocks to prevent getting outdated
>>  		 * rq clocks from a previous scx scheduler.
>>  		 */
>>  		scx_rq_clock_invalidate(rq);
>> -
>> -		/*
>> -		 * We are unloading the sched_ext scheduler, we do not need its
>> -		 * DL server bandwidth anymore, remove it for all CPUs. Whenever
>> -		 * the first SCX task is enqueued (when scx is re-loaded), its DL
>> -		 * server bandwidth will be re-initialized.
>> -		 */
>> -		rq_lock_irqsave(rq, &rf);
>> -		update_rq_clock(rq);
>> -		if (dl_server_active(&rq->ext_server))
>> -			dl_server_stop(&rq->ext_server);
>> -		dl_server_remove_params(&rq->ext_server);
>> -		rq_unlock_irqrestore(rq, &rf);
>>  	}
>
> We should probably remove this for_each_possible_cpu() completely.

Ah right, we only need to call scx_rq_clock_invalidate(rq); per its comment:

+		/*
+		 * Invalidate all the rq clocks to prevent getting outdated
+		 * rq clocks from a previous scx scheduler.
+		 */

So I'll get rid of it and run some tests, thanks!

 - Joel