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[87.16.204.193]) by smtp.gmail.com with ESMTPSA id c33sm1683018qtk.40.2020.07.24.08.31.58 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 24 Jul 2020 08:32:01 -0700 (PDT) Subject: Re: [PATCH] sched/deadline: dome some cleanup for push_dl_task() To: Juri Lelli , Peng Liu Cc: linux-kernel@vger.kernel.org, mingo@redhat.com, peterz@infradead.org, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de References: <20200706160442.GA19741@iZj6chx1xj0e0buvshuecpZ> <20200724071426.GD14912@localhost.localdomain> From: Daniel Bristot de Oliveira Message-ID: <16385ed9-eb44-3ea4-b10a-1e5ef993b33e@redhat.com> Date: Fri, 24 Jul 2020 17:31:56 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20200724071426.GD14912@localhost.localdomain> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/24/20 9:14 AM, Juri Lelli wrote: > Hi, > > On 07/07/20 00:04, Peng Liu wrote: >> 'commit 840d719604b0 ("sched/deadline: Update rq_clock of later_rq when pushing a task")' >> introduced the update_rq_clock() to fix the "used-before-update" bug. >> >> 'commit f4904815f97a ("sched/deadline: Fix double accounting of rq/running bw in push & pull")' >> took away the bug source(add_running_bw()). >> >> We no longer need to update rq_clock in advance, let activate_task() >> worry about that. >> >> Signed-off-by: Peng Liu >> --- >> kernel/sched/deadline.c | 8 +------- >> 1 file changed, 1 insertion(+), 7 deletions(-) >> >> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c >> index 504d2f51b0d6..c3fa11f84d93 100644 >> --- a/kernel/sched/deadline.c >> +++ b/kernel/sched/deadline.c >> @@ -2104,13 +2104,7 @@ static int push_dl_task(struct rq *rq) >> >> deactivate_task(rq, next_task, 0); >> set_task_cpu(next_task, later_rq->cpu); >> - >> - /* >> - * Update the later_rq clock here, because the clock is used >> - * by the cpufreq_update_util() inside __add_running_bw(). >> - */ >> - update_rq_clock(later_rq); >> - activate_task(later_rq, next_task, ENQUEUE_NOCLOCK); >> + activate_task(later_rq, next_task, 0); >> ret = 1; > The change looks good to me, since now add_running_bw() is called later > by enqueue_task_dl(), but rq_clock has already been updated by core's > enqueue_task(). > > Daniel, Dietmar, a second pair of eyes (since you authored the commits > above)? > > I'd chage subject to something like "sched/deadline: Stop updating > rq_clock before pushing a task". Looks good to me! Acked-by: Daniel Bristot de Oliveira Thanks -- Daniel