From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753696AbaIPLaS (ORCPT ); Tue, 16 Sep 2014 07:30:18 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:40685 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752833AbaIPLaQ (ORCPT ); Tue, 16 Sep 2014 07:30:16 -0400 Message-ID: <54181F34.5000406@linux.vnet.ibm.com> Date: Tue, 16 Sep 2014 16:59:56 +0530 From: Preeti U Murthy User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Kirill Tkhai , preeti@linux.vnet.ibm.com CC: LKML , Peter Zijlstra , Ingo Molnar , Kirill Tkhai Subject: Re: [PATCH] sched: Do not stop cpu in set_cpus_allowed_ptr() if task is not running References: <1410519814.3569.7.camel@tkhai> <1410775350.3569.51.camel@tkhai> In-Reply-To: <1410775350.3569.51.camel@tkhai> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-TM-AS-MML: disable X-Content-Scanned: Fidelis XPS MAILER x-cbid: 14091611-1344-0000-0000-0000043B2B70 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/15/2014 03:32 PM, Kirill Tkhai wrote: > Hi, Preeti, > > В Пн, 15/09/2014 в 15:18 +0530, Preeti Murthy пишет: >> Hi Kirill, >> >> Which tree is this patch based on? __migrate_task() does a >> double_rq_lock/unlock() today in mainline, doesn't it? I don't >> however see that in your patch. > > it's based on recent tip tree: > https://git.kernel.org/cgit/linux/kernel/git/tip/tip.git/ > > Also, once I received a build-robot message about my patch > makes warning on allyesconfig, and since that time I learned > about Peter's tree :) > > https://git.kernel.org/cgit/linux/kernel/git/peterz/queue.git > > (This is for info, I don't know if it is right to make patches > based on in. But really good if you was away for some time > and you're interested in recent news without lkml archive reading. > I use it :) Ok I checked the patch against tip tree and the patch looks good to me. Reviewed-by; Preeti U Murthy Thanks! Regards Preeti U Murthy > > Regards, > Kirill > >> On Fri, Sep 12, 2014 at 4:33 PM, Kirill Tkhai wrote: >>> >>> If a task is queued but not running on it rq, we can simply migrate >>> it without migration thread and switching of context. >>> >>> Signed-off-by: Kirill Tkhai >>> --- >>> kernel/sched/core.c | 47 ++++++++++++++++++++++++++++++++--------------- >>> 1 file changed, 32 insertions(+), 15 deletions(-) >>> >>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c >>> index d4399b4..dbbba26 100644 >>> --- a/kernel/sched/core.c >>> +++ b/kernel/sched/core.c >>> @@ -4594,6 +4594,33 @@ void init_idle(struct task_struct *idle, int cpu) >>> } >>> >>> #ifdef CONFIG_SMP >>> +/* >>> + * move_queued_task - move a queued task to new rq. >>> + * >>> + * Returns (locked) new rq. Old rq's lock is released. >>> + */ >>> +static struct rq *move_queued_task(struct task_struct *p, int new_cpu) >>> +{ >>> + struct rq *rq = task_rq(p); >>> + >>> + lockdep_assert_held(&rq->lock); >>> + >>> + dequeue_task(rq, p, 0); >>> + p->on_rq = TASK_ON_RQ_MIGRATING; >>> + set_task_cpu(p, new_cpu); >>> + raw_spin_unlock(&rq->lock); >>> + >>> + rq = cpu_rq(new_cpu); >>> + >>> + raw_spin_lock(&rq->lock); >>> + BUG_ON(task_cpu(p) != new_cpu); >>> + p->on_rq = TASK_ON_RQ_QUEUED; >>> + enqueue_task(rq, p, 0); >>> + check_preempt_curr(rq, p, 0); >>> + >>> + return rq; >>> +} >>> + >>> void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) >>> { >>> if (p->sched_class && p->sched_class->set_cpus_allowed) >>> @@ -4650,14 +4677,15 @@ int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) >>> goto out; >>> >>> dest_cpu = cpumask_any_and(cpu_active_mask, new_mask); >>> - if (task_on_rq_queued(p) || p->state == TASK_WAKING) { >>> + if (task_running(rq, p) || p->state == TASK_WAKING) { >>> struct migration_arg arg = { p, dest_cpu }; >>> /* Need help from migration thread: drop lock and wait. */ >>> task_rq_unlock(rq, p, &flags); >>> stop_one_cpu(cpu_of(rq), migration_cpu_stop, &arg); >>> tlb_migrate_finish(p->mm); >>> return 0; >>> - } >>> + } else if (task_on_rq_queued(p)) >>> + rq = move_queued_task(p, dest_cpu); >>> out: >>> task_rq_unlock(rq, p, &flags); >>> >>> @@ -4700,19 +4728,8 @@ static int __migrate_task(struct task_struct *p, int src_cpu, int dest_cpu) >>> * If we're not on a rq, the next wake-up will ensure we're >>> * placed properly. >>> */ >>> - if (task_on_rq_queued(p)) { >>> - dequeue_task(rq, p, 0); >>> - p->on_rq = TASK_ON_RQ_MIGRATING; >>> - set_task_cpu(p, dest_cpu); >>> - raw_spin_unlock(&rq->lock); >>> - >>> - rq = cpu_rq(dest_cpu); >>> - raw_spin_lock(&rq->lock); >>> - BUG_ON(task_rq(p) != rq); >>> - p->on_rq = TASK_ON_RQ_QUEUED; >>> - enqueue_task(rq, p, 0); >>> - check_preempt_curr(rq, p, 0); >>> - } >>> + if (task_on_rq_queued(p)) >>> + rq = move_queued_task(p, dest_cpu); >>> done: >>> ret = 1; >>> fail: >>> >>> >>> >>> -- >>> To unsubscribe from this list: send the line "unsubscribe linux-kernel" in >>> the body of a message to majordomo@vger.kernel.org >>> More majordomo info at http://vger.kernel.org/majordomo-info.html >>> Please read the FAQ at http://www.tux.org/lkml/ > >