linux-kernel - [tip:sched/core] sched/core: Check for available DL bandwidth in cpuset_cpu

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Message-ID: <tip-3c18d447b3b36a8d3c90dc37dfbd363cdb685d0a@git.kernel.org>
Date:	Thu, 2 Apr 2015 11:47:04 -0700
From:	tip-bot for Juri Lelli <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, juri.lelli@...il.com,
	peterz@...radead.org, tglx@...utronix.de, juri.lelli@....com,
	mingo@...nel.org, hpa@...or.com
Subject: [tip:sched/core] sched/core:
  Check for available DL bandwidth in cpuset_cpu_inactive()

Commit-ID:  3c18d447b3b36a8d3c90dc37dfbd363cdb685d0a
Gitweb:     http://git.kernel.org/tip/3c18d447b3b36a8d3c90dc37dfbd363cdb685d0a
Author:     Juri Lelli <juri.lelli@....com>
AuthorDate: Tue, 31 Mar 2015 09:53:37 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Thu, 2 Apr 2015 17:42:56 +0200

sched/core: Check for available DL bandwidth in cpuset_cpu_inactive()

Hotplug operations are destructive w.r.t. cpusets. In case such an
operation is performed on a CPU belonging to an exlusive cpuset, the
DL bandwidth information associated with the corresponding root
domain is gone even if the operation fails (in sched_cpu_inactive()).

For this reason we need to move the check we currently have in
sched_cpu_inactive() to cpuset_cpu_inactive() to prevent useless
cpusets reconfiguration in the CPU_DOWN_FAILED path.

Signed-off-by: Juri Lelli <juri.lelli@....com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Juri Lelli <juri.lelli@...il.com>
Link: http://lkml.kernel.org/r/1427792017-7356-2-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 kernel/sched/core.c | 56 ++++++++++++++++++++++++++---------------------------
 1 file changed, 28 insertions(+), 28 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4c49e75..28b0d75 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -5337,36 +5337,13 @@ static int sched_cpu_active(struct notifier_block *nfb,
 static int sched_cpu_inactive(struct notifier_block *nfb,
 					unsigned long action, void *hcpu)
 {
-	unsigned long flags;
-	long cpu = (long)hcpu;
-	struct dl_bw *dl_b;
-
 	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_DOWN_PREPARE:
-		set_cpu_active(cpu, false);
-
-		/* explicitly allow suspend */
-		if (!(action & CPU_TASKS_FROZEN)) {
-			bool overflow;
-			int cpus;
-
-			rcu_read_lock_sched();
-			dl_b = dl_bw_of(cpu);
-
-			raw_spin_lock_irqsave(&dl_b->lock, flags);
-			cpus = dl_bw_cpus(cpu);
-			overflow = __dl_overflow(dl_b, cpus, 0, 0);
-			raw_spin_unlock_irqrestore(&dl_b->lock, flags);
-
-			rcu_read_unlock_sched();
-
-			if (overflow)
-				return notifier_from_errno(-EBUSY);
-		}
+		set_cpu_active((long)hcpu, false);
 		return NOTIFY_OK;
+	default:
+		return NOTIFY_DONE;
 	}
-
-	return NOTIFY_DONE;
 }
 
 static int __init migration_init(void)
@@ -7006,7 +6983,6 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
 		 */
 
 	case CPU_ONLINE:
-	case CPU_DOWN_FAILED:
 		cpuset_update_active_cpus(true);
 		break;
 	default:
@@ -7018,8 +6994,32 @@ static int cpuset_cpu_active(struct notifier_block *nfb, unsigned long action,
 static int cpuset_cpu_inactive(struct notifier_block *nfb, unsigned long action,
 			       void *hcpu)
 {
-	switch (action) {
+	unsigned long flags;
+	long cpu = (long)hcpu;
+	struct dl_bw *dl_b;
+
+	switch (action & ~CPU_TASKS_FROZEN) {
 	case CPU_DOWN_PREPARE:
+		/* explicitly allow suspend */
+		if (!(action & CPU_TASKS_FROZEN)) {
+			bool overflow;
+			int cpus;
+
+			rcu_read_lock_sched();
+			dl_b = dl_bw_of(cpu);
+
+			raw_spin_lock_irqsave(&dl_b->lock, flags);
+			cpus = dl_bw_cpus(cpu);
+			overflow = __dl_overflow(dl_b, cpus, 0, 0);
+			raw_spin_unlock_irqrestore(&dl_b->lock, flags);
+
+			rcu_read_unlock_sched();
+
+			if (overflow) {
+				trace_printk("hotplug failed for cpu %lu", cpu);
+				return notifier_from_errno(-EBUSY);
+			}
+		}
 		cpuset_update_active_cpus(false);
 		break;
 	case CPU_DOWN_PREPARE_FROZEN:
--
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