do CPU_DEAD migrating under read_lock(tasklist) instead of write_lock_irq(tasklist)
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 <oleg@tv-sign.ru>
Cc: Cliff Wickman <cpw@sgi.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Akinobu Mita <akinobu.mita@gmail.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 0da2b26..c747bc9 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5060,6 +5060,17 @@
}
#ifdef CONFIG_HOTPLUG_CPU
+
+static int __migrate_task_irq(struct task_struct *p, int src_cpu, int dest_cpu)
+{
+ int ret;
+
+ local_irq_disable();
+ ret = __migrate_task(p, src_cpu, dest_cpu);
+ local_irq_enable();
+ return ret;
+}
+
/*
* Figure out where task on dead CPU should go, use force if neccessary.
* NOTE: interrupts should be disabled by the caller
@@ -5098,7 +5109,7 @@
"longer affine to cpu%d\n",
p->pid, p->comm, dead_cpu);
}
- } while (!__migrate_task(p, dead_cpu, dest_cpu));
+ } while (!__migrate_task_irq(p, dead_cpu, dest_cpu));
}
/*
@@ -5126,7 +5137,7 @@
{
struct task_struct *p, *t;
- write_lock_irq(&tasklist_lock);
+ read_lock(&tasklist_lock);
do_each_thread(t, p) {
if (p == current)
@@ -5136,7 +5147,7 @@
move_task_off_dead_cpu(src_cpu, p);
} while_each_thread(t, p);
- write_unlock_irq(&tasklist_lock);
+ read_unlock(&tasklist_lock);
}
/*
@@ -5214,11 +5225,10 @@
* 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);
}
