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Message-ID: <1462981808.23934.145.camel@edumazet-glaptop3.roam.corp.google.com>
Subject: Re: [RFC PATCH 0/2] net: threadable napi poll loop
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Eric Dumazet <edumazet@google.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>,
        Peter Zijlstra <peterz@infradead.org>, Paolo Abeni <pabeni@redhat.com>,
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        Tom Herbert <tom@herbertland.com>, Ingo Molnar <mingo@kernel.org>,
        Rik van Riel <riel@redhat.com>, LKML <linux-kernel@vger.kernel.org>
Date: Wed, 11 May 2016 08:50:08 -0700
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On Wed, 2016-05-11 at 07:40 -0700, Eric Dumazet wrote:
> On Wed, May 11, 2016 at 6:13 AM, Hannes Frederic Sowa
> <hannes@stressinduktion.org> wrote:
> 
> > This looks racy to me as the ksoftirqd could be in the progress to stop
> > and we would miss another softirq invocation.
> 
> Looking at smpboot_thread_fn(), it looks fine :
> 
>                 if (!ht->thread_should_run(td->cpu)) {
>                         preempt_enable_no_resched();
>                         schedule();
>                 } else {
>                         __set_current_state(TASK_RUNNING);
>                         preempt_enable();
>                         ht->thread_fn(td->cpu);
>                 }

BTW, I wonder why we pass td->cpu as argument to ht->thread_fn(td->cpu)

This always should be the current processor id.

Or do we have an issue because we ignore it in :

static int ksoftirqd_should_run(unsigned int cpu)
{
        return local_softirq_pending();
}