Eliminate lock_cpu_hotplug in kernel/schedc
Eliminate lock_cpu_hotplug from kernel/sched.c and use sched_hotcpu_mutex
instead to postpone a hotplug event.
In the migration_call hotcpu callback function, take sched_hotcpu_mutex
while handling the event CPU_LOCK_ACQUIRE and release it while handling
CPU_LOCK_RELEASE event.
[akpm@linux-foundation.org: fix deadlock]
Signed-off-by: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/kernel/sched.c b/kernel/sched.c
index 66bd7ff..fe1a9c2 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -305,6 +305,7 @@
};
static DEFINE_PER_CPU(struct rq, runqueues) ____cacheline_aligned_in_smp;
+static DEFINE_MUTEX(sched_hotcpu_mutex);
static inline int cpu_of(struct rq *rq)
{
@@ -4520,13 +4521,13 @@
struct task_struct *p;
int retval;
- lock_cpu_hotplug();
+ mutex_lock(&sched_hotcpu_mutex);
read_lock(&tasklist_lock);
p = find_process_by_pid(pid);
if (!p) {
read_unlock(&tasklist_lock);
- unlock_cpu_hotplug();
+ mutex_unlock(&sched_hotcpu_mutex);
return -ESRCH;
}
@@ -4553,7 +4554,7 @@
out_unlock:
put_task_struct(p);
- unlock_cpu_hotplug();
+ mutex_unlock(&sched_hotcpu_mutex);
return retval;
}
@@ -4610,7 +4611,7 @@
struct task_struct *p;
int retval;
- lock_cpu_hotplug();
+ mutex_lock(&sched_hotcpu_mutex);
read_lock(&tasklist_lock);
retval = -ESRCH;
@@ -4626,7 +4627,7 @@
out_unlock:
read_unlock(&tasklist_lock);
- unlock_cpu_hotplug();
+ mutex_unlock(&sched_hotcpu_mutex);
if (retval)
return retval;
@@ -5388,6 +5389,10 @@
struct rq *rq;
switch (action) {
+ case CPU_LOCK_ACQUIRE:
+ mutex_lock(&sched_hotcpu_mutex);
+ break;
+
case CPU_UP_PREPARE:
p = kthread_create(migration_thread, hcpu, "migration/%d",cpu);
if (IS_ERR(p))
@@ -5433,7 +5438,7 @@
BUG_ON(rq->nr_running != 0);
/* No need to migrate the tasks: it was best-effort if
- * they didn't do lock_cpu_hotplug(). Just wake up
+ * they didn't take sched_hotcpu_mutex. Just wake up
* the requestors. */
spin_lock_irq(&rq->lock);
while (!list_empty(&rq->migration_queue)) {
@@ -5447,6 +5452,9 @@
spin_unlock_irq(&rq->lock);
break;
#endif
+ case CPU_LOCK_RELEASE:
+ mutex_unlock(&sched_hotcpu_mutex);
+ break;
}
return NOTIFY_OK;
}
@@ -6822,10 +6830,10 @@
{
int err;
- lock_cpu_hotplug();
+ mutex_lock(&sched_hotcpu_mutex);
detach_destroy_domains(&cpu_online_map);
err = arch_init_sched_domains(&cpu_online_map);
- unlock_cpu_hotplug();
+ mutex_unlock(&sched_hotcpu_mutex);
return err;
}
@@ -6930,12 +6938,12 @@
{
cpumask_t non_isolated_cpus;
- lock_cpu_hotplug();
+ mutex_lock(&sched_hotcpu_mutex);
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);
- unlock_cpu_hotplug();
+ mutex_unlock(&sched_hotcpu_mutex);
/* XXX: Theoretical race here - CPU may be hotplugged now */
hotcpu_notifier(update_sched_domains, 0);
