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

From: yjin
Date: Sat Nov 14 2015 - 00:14:27 EST



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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