linux-kernel - Re: [PATCH V3] Softirq:avoid large sched delay from the pending softirqs

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Message-ID: <CAKc596LwF3UNrasZcm46wQX8JSEht4oxx+sDqRKfSkM3Ld0Fjw@mail.gmail.com>
Date:   Thu, 23 Jul 2020 22:11:59 +0800
From:   jun qian <qianjun.kernel@...il.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     peterz@...radead.org, will@...nel.org, luto@...nel.org,
        Uladzislau Rezki <urezki@...il.com>,
        linux-kernel@...r.kernel.org, Yafang Shao <laoar.shao@...il.com>
Subject: Re: [PATCH V3] Softirq:avoid large sched delay from the pending softirqs

On Thu, Jul 23, 2020 at 9:41 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> qianjun.kernel@...il.com writes:
> > From: jun qian <qianjun.kernel@...il.com>
> > +             /*
> > +              * the softirq's action has been running for too much time
> > +              * so it may need to wakeup the ksoftirqd
> > +              */
> > +             if (need_resched() && ktime_get() > end)
> > +                     break;
>
> As per my reply on V2 this is leaking non handled pending bits. If you
> do a V4, can you please use sched_clock() instead of ktime_get()?
>
The reason why the non handled pending bits leaked is
set_softirq_pending(0) called in the start, if the
loop is broken, the not handled bit will leak. This is my
understanding, I am not sure if it is correct or not.
Looking forward to your reply.

Thank you so much.

> Thanks,
>
>         tglx