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

[yjin]

On 2015å11æ14æ 12:25, Steven Rostedt wrote:
> On Sat, 14 Nov 2015 10:53:18 +0800
> <yanjiang.jin@xxxxxxxxxxxxx> wrote:
>
> > From: Yanjiang Jin <yanjiang.jin@xxxxxxxxxxxxx>
> >
> > 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

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