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SubjectRe: [PATCH 4/9] softirq: Allow early break
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On 2023/5/5 20:10, Eric Dumazet wrote:
> On Fri, May 5, 2023 at 1:24 PM Liu Jian <liujian56@huawei.com> wrote:
>>
>> From: Peter Zijlstra <peterz@infradead.org>
>>
>> Allow terminating the softirq processing loop without finishing the
>> vectors.
>>
>> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>> Signed-off-by: Liu Jian <liujian56@huawei.com>
>> ---
>> 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)
>
>
Yes, we need to record the softirq that is not executed and continue
next time. I will fix it in next version.
Thanks.
>
>
>> }
>>
>> 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
>>

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