cpu-hotplug: replace per-subsystem mutexes with get_online_cpus()

This patch converts the known per-subsystem mutexes to get_online_cpus
put_online_cpus. It also eliminates the CPU_LOCK_ACQUIRE and
CPU_LOCK_RELEASE hotplug notification events.

Signed-off-by: Gautham  R Shenoy <ego@in.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 9 insertions, 16 deletions

diff --git a/kernel/sched.c b/kernel/sched.c
index 672aa68bfeac..c0e2db683e29 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -439,7 +439,6 @@ struct rq {
 };
 
 static DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues);
-static DEFINE_MUTEX(sched_hotcpu_mutex);
 
 static inline void check_preempt_curr(struct rq *rq, struct task_struct *p)
 {
@@ -4546,13 +4545,13 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
         struct task_struct *p;
         int retval;
 
-        mutex_lock(&sched_hotcpu_mutex);
+        get_online_cpus();
         read_lock(&tasklist_lock);
 
         p = find_process_by_pid(pid);
         if (!p) {
                 read_unlock(&tasklist_lock);
-                mutex_unlock(&sched_hotcpu_mutex);
+                put_online_cpus();
                 return -ESRCH;
         }
 
@@ -4592,7 +4591,7 @@ long sched_setaffinity(pid_t pid, cpumask_t new_mask)
         }
 out_unlock:
         put_task_struct(p);
-        mutex_unlock(&sched_hotcpu_mutex);
+        put_online_cpus();
         return retval;
 }
 
@@ -4649,7 +4648,7 @@ long sched_getaffinity(pid_t pid, cpumask_t *mask)
         struct task_struct *p;
         int retval;
 
-        mutex_lock(&sched_hotcpu_mutex);
+        get_online_cpus();
         read_lock(&tasklist_lock);
 
         retval = -ESRCH;
@@ -4665,7 +4664,7 @@ long sched_getaffinity(pid_t pid, cpumask_t *mask)
 
 out_unlock:
         read_unlock(&tasklist_lock);
-        mutex_unlock(&sched_hotcpu_mutex);
+        put_online_cpus();
 
         return retval;
 }
@@ -5625,9 +5624,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
         struct rq *rq;
 
         switch (action) {
-        case CPU_LOCK_ACQUIRE:
-                mutex_lock(&sched_hotcpu_mutex);
-                break;
 
         case CPU_UP_PREPARE:
         case CPU_UP_PREPARE_FROZEN:
@@ -5697,9 +5693,6 @@ migration_call(struct notifier_block *nfb, unsigned long action, void *hcpu)
                 spin_unlock_irq(&rq->lock);
                 break;
 #endif
-        case CPU_LOCK_RELEASE:
-                mutex_unlock(&sched_hotcpu_mutex);
-                break;
         }
         return NOTIFY_OK;
 }
@@ -6655,10 +6648,10 @@ static int arch_reinit_sched_domains(void)
 {
         int err;
 
-        mutex_lock(&sched_hotcpu_mutex);
+        get_online_cpus();
         detach_destroy_domains(&cpu_online_map);
         err = arch_init_sched_domains(&cpu_online_map);
-        mutex_unlock(&sched_hotcpu_mutex);
+        put_online_cpus();
 
         return err;
 }
@@ -6769,12 +6762,12 @@ void __init sched_init_smp(void)
 {
         cpumask_t non_isolated_cpus;
 
-        mutex_lock(&sched_hotcpu_mutex);
+        get_online_cpus();
         arch_init_sched_domains(&cpu_online_map);
         cpus_andnot(non_isolated_cpus, cpu_possible_map, cpu_isolated_map);
         if (cpus_empty(non_isolated_cpus))
                 cpu_set(smp_processor_id(), non_isolated_cpus);
-        mutex_unlock(&sched_hotcpu_mutex);
+        put_online_cpus();
         /* XXX: Theoretical race here - CPU may be hotplugged now */
         hotcpu_notifier(update_sched_domains, 0);