On Tue, May 10, 2016 at 03:51:37PM -0700, Eric Dumazet wrote:
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 17caf4b63342..22463217e3cf 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -56,6 +56,7 @@ EXPORT_SYMBOL(irq_stat);
> static struct softirq_action softirq_vec[NR_SOFTIRQS]
> __cacheline_aligned_in_smp;
>
> DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
> +DEFINE_PER_CPU(bool, ksoftirqd_scheduled);
>
> const char * const softirq_to_name[NR_SOFTIRQS] = {
> "HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "BLOCK_IOPOLL",
> @@ -73,8 +74,10 @@ static void wakeup_softirqd(void)
> /* Interrupts are disabled: no need to stop preemption */
> struct task_struct *tsk = __this_cpu_read(ksoftirqd);
>
> - if (tsk && tsk->state != TASK_RUNNING)
> + if (tsk && tsk->state != TASK_RUNNING) {
> + __this_cpu_write(ksoftirqd_scheduled, true);
> wake_up_process(tsk);
Since we're already looking at tsk->state, and the wake_up_process()
ensures the thing becomes TASK_RUNNING, you could add:
static inline bool ksoftirqd_running(void)
{
return __this_cpu_read(ksoftirqd)->state == TASK_RUNNING;
}
> + }
> }
>
> /*
> @@ -162,7 +165,9 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int
> cnt)
> */
> preempt_count_sub(cnt - 1);
>
> - if (unlikely(!in_interrupt() && local_softirq_pending())) {
> + if (unlikely(!in_interrupt() &&
> + local_softirq_pending() &&
> + !__this_cpu_read(ksoftirqd_scheduled))) {
And use it here,
> /*
> * Run softirq if any pending. And do it in its own stack
> * as we may be calling this deep in a task call stack already.
> @@ -340,6 +345,9 @@ void irq_enter(void)
>
> static inline void invoke_softirq(void)
> {
> + if (__this_cpu_read(ksoftirqd_scheduled))
and here.
> + return;
> +
> if (!force_irqthreads) {
> #ifdef CONFIG_HAVE_IRQ_EXIT_ON_IRQ_STACK
> /*
> @@ -660,6 +668,8 @@ static void run_ksoftirqd(unsigned int cpu)
> * in the task stack here.
> */
> __do_softirq();
> + if (!local_softirq_pending())
> + __this_cpu_write(ksoftirqd_scheduled, false);
And avoid twiddling the new variable which only seems to mirror
tsk->state.
> local_irq_enable();
> cond_resched_rcu_qs();
> return;
>
>
