Re: [RT PATCH] sched: rt: fix two possible deadlocks in push_irq_work_func

[yjin <yanjiang.jin@windriver.com>]

On 2015年11月14日 12:25, Steven Rostedt wrote:
> On Sat, 14 Nov 2015 10:53:18 +0800
> <yanjiang.jin@windriver.com> wrote:
>
>> From: Yanjiang Jin <yanjiang.jin@windriver.com>
>>
>> This can only happen in RT kernel due to run_timer_softirq() calls
>> irq_work_tick() when CONFIG_PREEMPT_RT_FULL is enabled as below:
>>
>> static void run_timer_softirq(struct softirq_action *h)
>> {
>> ........
>> if defined(CONFIG_IRQ_WORK) && defined(CONFIG_PREEMPT_RT_FULL)
>>          irq_work_tick();
>> endif
>> ........
>> }
>>
>> Use raw_spin_{un,}lock_irq{save,restore} in push_irq_work_func() to
>> prevent following potentially deadlock scenario:
> Ug. No, the real fix is that the irq work is to be run from hard
> interrupt context.
But if so, we shouldn't call irq_work_tick() in run_timer_softirq(), right?

Thanks!
Yanjiang
> Moving the scheduling of high priority real-time
> tasks to ksoftirqd defeats the purpose. The question is, why is that
> irq work being run from thread context when it has the
> IRQ_WORK_HARD_IRQ flag set?
>
> -- Steve
>