From df232437710122fcb4e4a0484a1eded5aec29a6a Mon Sep 17 00:00:00 2001 From: Caesar Wang Date: Tue, 23 Aug 2016 11:47:02 +0100 Subject: [PATCH] sched/fair: remove printk while schedule is in progress It will cause deadlock and while(1) if call printk while schedule is in progress. The block state like as below: cpu0(hold the console sem): printk->console_unlock->up_sem->spin_lock(&sem->lock)->wake_up_process(cpu1) ->try_to_wake_up(cpu1)->while(p->on_cpu). cpu1(request console sem): console_lock->down_sem->schedule->idle_banlance->update_cpu_capacity-> printk->console_trylock->spin_lock(&sem->lock). p->on_cpu will be 1 forever, because the task is still running on cpu1, so cpu0 is blocked in while(p->on_cpu), but cpu1 could not get spin_lock(&sem->lock), it is blocked too, it means the task will running on cpu1 forever. Signed-off-by: Caesar Wang --- kernel/sched/fair.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 7e42cd11e430..6b881cf81d79 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -7089,7 +7089,8 @@ static void update_cpu_capacity(struct sched_domain *sd, int cpu) mcc->cpu = cpu; #ifdef CONFIG_SCHED_DEBUG raw_spin_unlock_irqrestore(&mcc->lock, flags); - pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity); + printk_deferred(KERN_INFO "CPU%d: update max cpu_capacity %lu\n", + cpu, capacity); goto skip_unlock; #endif } -- 2.20.1