On Thu, 2015-04-16 at 18:28 +0200, Jan Kiszka wrote:
> Instead of turning all irq_work requests into lazy ones on -rt, just
> move their execution from hard into soft-irq context.
>
> This resolves deadlocks of ftrace which will queue work from
> arbitrary
> contexts, including those that have locks held that are needed for
> raising a soft-irq.
Yup, trace-cmd record -> dead-box fully repeatable, and now fixed.
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
>
> Second try, looks much better so far. And it also removes my concerns
> regarding other potential cases besides ftrace.
>
> kernel/irq_work.c | 26 ++++++++++----------------
> 1 file changed, 10 insertions(+), 16 deletions(-)
>
> diff --git a/kernel/irq_work.c b/kernel/irq_work.c
> index 9dda38a..3f6ffcd 100644
> --- a/kernel/irq_work.c
> +++ b/kernel/irq_work.c
> @@ -85,12 +85,9 @@ bool irq_work_queue_on(struct irq_work *work, int
> cpu)
> raise_irqwork = llist_add(&work->llnode,
> &per_cpu(hirq_work_list, cpu));
> else
> - raise_irqwork = llist_add(&work->llnode,
> - &per_cpu(lazy_list, cpu));
> -#else
> +#endif
> raise_irqwork = llist_add(&work->llnode,
> &per_cpu(raised_list, cpu));
> -#endif
>
> if (raise_irqwork)
> arch_send_call_function_single_ipi(cpu);
> @@ -114,21 +111,20 @@ bool irq_work_queue(struct irq_work *work)
> if (work->flags & IRQ_WORK_HARD_IRQ) {
> if (llist_add(&work->llnode, this_cpu_ptr(&hirq_work_list)))
> arch_irq_work_raise();
> - } else {
> + } else
> +#endif
> + if (work->flags & IRQ_WORK_LAZY) {
> if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
> tick_nohz_tick_stopped())
> +#ifdef CONFIG_PREEMPT_RT_FULL
> raise_softirq(TIMER_SOFTIRQ);
> - }
> #else
> - if (work->flags & IRQ_WORK_LAZY) {
> - if (llist_add(&work->llnode, this_cpu_ptr(&lazy_list)) &&
> - tick_nohz_tick_stopped())
> arch_irq_work_raise();
> +#endif
> } else {
> if (llist_add(&work->llnode, this_cpu_ptr(&raised_list)))
> arch_irq_work_raise();
> }
> -#endif
>
> preempt_enable();
>
> @@ -202,6 +198,8 @@ void irq_work_run(void)
> {
> #ifdef CONFIG_PREEMPT_RT_FULL
> irq_work_run_list(this_cpu_ptr(&hirq_work_list));
> + if (!llist_empty(this_cpu_ptr(&raised_list)))
> + raise_softirq(TIMER_SOFTIRQ);
> #else
> irq_work_run_list(this_cpu_ptr(&raised_list));
> irq_work_run_list(this_cpu_ptr(&lazy_list));
> @@ -211,15 +209,11 @@ EXPORT_SYMBOL_GPL(irq_work_run);
>
> void irq_work_tick(void)
> {
> -#ifdef CONFIG_PREEMPT_RT_FULL
> - irq_work_run_list(this_cpu_ptr(&lazy_list));
> -#else
> - struct llist_head *raised = &__get_cpu_var(raised_list);
> + struct llist_head *raised = this_cpu_ptr(&raised_list);
>
> if (!llist_empty(raised) && !arch_irq_work_has_interrupt())
> irq_work_run_list(raised);
> - irq_work_run_list(&__get_cpu_var(lazy_list));
> -#endif
> + irq_work_run_list(this_cpu_ptr(&lazy_list));
> }
>
> /*
--
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