move_task_off_dead_cpu() requires interrupts to be disabled,
while migrate_dead() calls it with enabled interrupts.
Added appropriate comments to functions and added
BUG_ON(!irqs_disabled()) into double_rq_lock() and
double_lock_balance() which are the origin sources of such bugs.
Signed-Off-By: Kirill Korotaev <[email protected]>
--- ./kernel/sched.c.schedx 2006-11-08 17:44:15.000000000 +0300
+++ ./kernel/sched.c 2006-11-14 11:32:24.000000000 +0300
@@ -1942,6 +1942,7 @@ static void double_rq_lock(struct rq *rq
__acquires(rq1->lock)
__acquires(rq2->lock)
{
+ BUG_ON(!irqs_disabled());
if (rq1 == rq2) {
spin_lock(&rq1->lock);
__acquire(rq2->lock); /* Fake it out ;) */
@@ -1981,6 +1982,11 @@ static void double_lock_balance(struct r
__acquires(busiest->lock)
__acquires(this_rq->lock)
{
+ if (unlikely(!irqs_disabled())) {
+ /* printk() doesn't work good under rq->lock */
+ spin_unlock(&this_rq->lock);
+ BUG_ON(1);
+ }
if (unlikely(!spin_trylock(&busiest->lock))) {
if (busiest < this_rq) {
spin_unlock(&this_rq->lock);
@@ -5056,7 +5062,10 @@ wait_to_die:
}
#ifdef CONFIG_HOTPLUG_CPU
-/* Figure out where task on dead CPU should go, use force if neccessary. */
+/*
+ * Figure out where task on dead CPU should go, use force if neccessary.
+ * NOTE: interrupts should be disabled by the caller
+ */
static void move_task_off_dead_cpu(int dead_cpu, struct task_struct *p)
{
unsigned long flags;
@@ -5176,6 +5185,7 @@ void idle_task_exit(void)
mmdrop(mm);
}
+/* called under rq->lock with disabled interrupts */
static void migrate_dead(unsigned int dead_cpu, struct task_struct *p)
{
struct rq *rq = cpu_rq(dead_cpu);
@@ -5192,10 +5202,11 @@ static void migrate_dead(unsigned int de
* Drop lock around migration; if someone else moves it,
* that's OK. No task can be added to this CPU, so iteration is
* fine.
+ * NOTE: interrupts should be left disabled --dev@
*/
- spin_unlock_irq(&rq->lock);
+ spin_unlock(&rq->lock);
move_task_off_dead_cpu(dead_cpu, p);
- spin_lock_irq(&rq->lock);
+ spin_lock(&rq->lock);
put_task_struct(p);
}
-
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