(the explicit ack/nack from maintainers is wanted)
Currently move_task_off_dead_cpu() is called under write_lock_irq(tasklist).
This means it can't use task_lock() which is needed to improve migrating to
take task's ->cpuset into account.
Change the code to call move_task_off_dead_cpu() with irqs enabled, and change
migrate_live_tasks() to use read_lock(tasklist).
This all is a preparation for the futher changes proposed by Cliff Wickman, see
http://marc.info/?t=117327786100003
Signed-off-by: Oleg Nesterov <[email protected]>
--- t/kernel/sched.c~1_READ_LOCK 2007-08-12 14:15:37.000000000 +0400
+++ t/kernel/sched.c 2007-08-24 20:31:03.000000000 +0400
@@ -5048,7 +5048,7 @@ static void move_task_off_dead_cpu(int d
unsigned long flags;
cpumask_t mask;
struct rq *rq;
- int dest_cpu;
+ int dest_cpu, done;
restart:
/* On same node? */
@@ -5077,7 +5077,11 @@ restart:
"longer affine to cpu%d\n",
p->pid, p->comm, dead_cpu);
}
- if (!__migrate_task(p, dead_cpu, dest_cpu))
+
+ local_irq_disable();
+ done = __migrate_task(p, dead_cpu, dest_cpu);
+ local_irq_enable();
+ if (!done)
goto restart;
}
@@ -5106,7 +5110,7 @@ static void migrate_live_tasks(int src_c
{
struct task_struct *p, *t;
- write_lock_irq(&tasklist_lock);
+ read_lock(&tasklist_lock);
do_each_thread(t, p) {
if (p == current)
@@ -5116,7 +5120,7 @@ static void migrate_live_tasks(int src_c
move_task_off_dead_cpu(src_cpu, p);
} while_each_thread(t, p);
- write_unlock_irq(&tasklist_lock);
+ read_unlock(&tasklist_lock);
}
/*
@@ -5180,11 +5184,10 @@ 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(&rq->lock);
+ spin_unlock_irq(&rq->lock);
move_task_off_dead_cpu(dead_cpu, p);
- spin_lock(&rq->lock);
+ spin_lock_irq(&rq->lock);
put_task_struct(p);
}
-
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