From: Srivatsa Vaddagiri Fix a CPU Hotplug problem wherein idle task's "->prio" value is not restored to MAX_PRIO during CPU_DEAD handling. Without this patch, once a CPU is offlined and then later onlined, it becomes "more or less" useless (does not run any task other than its idle task!) Ingo said: The __setscheduler() call is (technically) incorrect because in the SCHED_NORMAL case the prio should be zero. So it's a bit cleaner to set up the static priority to MAX_PRIO and then revert the policy to SCHED_NORMAL via __setscheduler(). Signed-off-by: Ingo Molnar Signed-off-by: Andrew Morton --- 25-akpm/kernel/sched.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletion(-) diff -puN kernel/sched.c~restore-idle-tasks-priority-during-cpu_dead-notification kernel/sched.c --- 25/kernel/sched.c~restore-idle-tasks-priority-during-cpu_dead-notification Wed May 26 16:31:41 2004 +++ 25-akpm/kernel/sched.c Wed May 26 16:31:41 2004 @@ -3742,7 +3742,8 @@ static int migration_call(struct notifie /* Idle task back to normal (off runqueue, low prio) */ rq = task_rq_lock(rq->idle, &flags); deactivate_task(rq->idle, rq); - __setscheduler(rq->idle, SCHED_NORMAL, MAX_PRIO); + rq->idle->static_prio = MAX_PRIO; + __setscheduler(rq->idle, SCHED_NORMAL, 0); task_rq_unlock(rq, &flags); BUG_ON(rq->nr_running != 0); _