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ARM64: sched: fix bug: remove printk while schedule is in progress

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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.

Change-Id: I60d02d8c957273872f97939632bdd235accdad4e
Signed-off-by: Chen Liang <cl@rock-chips.com>
This commit is contained in:
Chen Liang 2016-07-08 10:37:53 +08:00 committed by Huang, Tao
parent 649f8c0d9a
commit 9aa987e461
1 changed files with 1 additions and 1 deletions
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2
kernel/sched/fair.c
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@ -6808,7 +6808,7 @@ 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);
//pr_info("CPU%d: update max cpu_capacity %lu\n", cpu, capacity);
goto skip_unlock;
#endif
}