Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756003AbaJXJRP (ORCPT ); Fri, 24 Oct 2014 05:17:15 -0400 Received: from service87.mimecast.com ([91.220.42.44]:37736 "EHLO service87.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751718AbaJXJQw (ORCPT ); Fri, 24 Oct 2014 05:16:52 -0400 From: Juri Lelli To: linux-kernel@vger.kernel.org, peterz@infradead.org Cc: juri.lelli@gmail.com, mingo@redhat.com, daniel.wagner@bmw-carit.de, vincent@legout.info, Juri Lelli , Dario Faggioli , Michael Trimarchi , Fabio Checconi , Li Zefan , cgroups@vger.kernel.org Subject: [PATCH 2/4] sched/deadline: ensure that updates to exclusive cpusets don't break AC Date: Fri, 24 Oct 2014 10:16:36 +0100 Message-Id: <1414142198-18552-3-git-send-email-juri.lelli@arm.com> X-Mailer: git-send-email 2.1.2 In-Reply-To: <1414142198-18552-1-git-send-email-juri.lelli@arm.com> References: <1414142198-18552-1-git-send-email-juri.lelli@arm.com> X-OriginalArrivalTime: 24 Oct 2014 09:16:50.0670 (UTC) FILETIME=[3E8868E0:01CFEF6B] X-MC-Unique: 114102410165017801 Content-Type: text/plain; charset=WINDOWS-1252 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by nfs id s9O9HK48022058 How we deal with updates to exclusive cpusets is currently broken. As an example, suppose we have an exclusive cpuset composed of two cpus: A[cpu0,cpu1]. We can assign SCHED_DEADLINE task to it up to the allowed bandwidth. If we want now to modify cpusetA's cpumask, we have to check that removing a cpu's amount of bandwidth doesn't break AC guarantees. This thing isn't checked in the current code. This patch fixes the problem above, denying an update if the new cpumask won't have enough bandwidth for SCHED_DEADLINE tasks that are currently active. Signed-off-by: Juri Lelli Reported-by: Peter Zijlstra Cc: Ingo Molnar Cc: Peter Zijlstra Cc: Juri Lelli Cc: Dario Faggioli Cc: Michael Trimarchi Cc: Fabio Checconi Cc: Li Zefan Cc: linux-kernel@vger.kernel.org Cc: cgroups@vger.kernel.org --- include/linux/sched.h | 2 ++ kernel/cpuset.c | 10 ++++++++++ kernel/sched/core.c | 21 +++++++++++++++++++++ 3 files changed, 33 insertions(+) diff --git a/include/linux/sched.h b/include/linux/sched.h index f225f20..d4ed0db 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2032,6 +2032,8 @@ static inline void tsk_restore_flags(struct task_struct *task, task->flags |= orig_flags & flags; } +extern int cpuset_cpumask_can_shrink(const struct cpumask *cur, + const struct cpumask *trial); extern int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed); #ifdef CONFIG_SMP diff --git a/kernel/cpuset.c b/kernel/cpuset.c index ab9be24..9066cc7 100644 --- a/kernel/cpuset.c +++ b/kernel/cpuset.c @@ -505,6 +505,16 @@ static int validate_change(struct cpuset *cur, struct cpuset *trial) goto out; } + /* + * We can't shrink if we won't have enough room for SCHED_DEADLINE + * tasks. + */ + ret = -EBUSY; + if (is_cpu_exclusive(cur) && + !cpuset_cpumask_can_shrink(cur->cpus_allowed, + trial->cpus_allowed)) + goto out; + ret = 0; out: rcu_read_unlock(); diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 07ec9bb..35674eb 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -4622,6 +4622,27 @@ void init_idle(struct task_struct *idle, int cpu) #endif } +int cpuset_cpumask_can_shrink(const struct cpumask *cur, + const struct cpumask *trial) +{ + int ret = 1, trial_cpus; + struct dl_bw *cur_dl_b; + unsigned long flags; + + rcu_read_lock_sched(); + cur_dl_b = dl_bw_of(cpumask_any(cur)); + trial_cpus = cpumask_weight(trial); + + raw_spin_lock_irqsave(&cur_dl_b->lock, flags); + if (cur_dl_b->bw != -1 && + cur_dl_b->bw * trial_cpus < cur_dl_b->total_bw) + ret = 0; + raw_spin_unlock_irqrestore(&cur_dl_b->lock, flags); + rcu_read_unlock_sched(); + + return ret; +} + int task_can_attach(struct task_struct *p, const struct cpumask *cs_cpus_allowed) { -- 2.1.2 -- 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/