On Fri, May 5, 2023 at 1:24 PM Liu Jian <liujian56@xxxxxxxxxx> wrote:
>
> From: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>
> Allow terminating the softirq processing loop without finishing the
> vectors.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
> Signed-off-by: Liu Jian <liujian56@xxxxxxxxxx>
> ---
> kernel/softirq.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index 48a81d8ae49a..e2cad5d108c8 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -582,6 +582,9 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
> prev_count, preempt_count());
> preempt_count_set(prev_count);
> }
> +
> + if (pending && __softirq_needs_break(start))
> + break;
This means that some softirq may starve, because
for_each_set_bit(vec_nr, &pending, NR_SOFTIRQS)
Always iterate using the same order (of bits)
> }
>
> if (!IS_ENABLED(CONFIG_PREEMPT_RT) &&
> @@ -590,13 +593,14 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
>
> local_irq_disable();
>
> - pending = local_softirq_pending();
> - if (pending) {
> - if (!__softirq_needs_break(start) && --max_restart)
> - goto restart;
> + if (pending)
> + or_softirq_pending(pending);
> + else if ((pending = local_softirq_pending()) &&
> + !__softirq_needs_break(start) &&
> + --max_restart)
> + goto restart;
>
> - wakeup_softirqd();
> - }
> + wakeup_softirqd();
>
> account_softirq_exit(current);
> lockdep_softirq_end(in_hardirq);
> --
> 2.34.1
>
