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@arm.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Juri Lelli <juri.lelli@gmail.com>
Link: http://lkml.kernel.org/r/1427792017-7356-2-git-send-email-juri.lelli@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

1 files changed, 28 insertions, 28 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 4c49e75ca24d..28b0d75a8273 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: