linux-kernel - Re: [PATCH] Fix lockup related to stop_machine being stuck in __do

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Date:	Thu, 6 Jun 2013 13:44:28 -0700
From:	Tejun Heo <tj@...nel.org>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	greearb@...delatech.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Fix lockup related to stop_machine being stuck in
 __do_softirq.

On Wed, Jun 05, 2013 at 09:29:54PM -0700, Eric Dumazet wrote:
> On Wed, 2013-06-05 at 21:25 -0700, greearb@...delatech.com wrote:
> > From: Ben Greear <greearb@...delatech.com>
> 
> > diff --git a/kernel/softirq.c b/kernel/softirq.c
> > index 14d7758..f150ad6 100644
> > --- a/kernel/softirq.c
> > +++ b/kernel/softirq.c
> > @@ -204,6 +204,7 @@ EXPORT_SYMBOL(local_bh_enable_ip);
> >   * should not be able to lock up the box.
> 
> Could you update the comment ?
> 
> I had the following :
> 
> - * We restart softirq processing for at most 2 ms,
> - * and if need_resched() is not set.
> + * We restart softirq processing for at most MAX_SOFTIRQ_RESTART times,
> + * but break the loop if need_resched() is set or after 2 ms.

It'd be nice to briefly explain why both protections are necessary in
the comment and maybe cite this thread.  Also, please cc Linus when
posting the next round and I think we still want to find out what's
going on with infinite softirq, I'll reply in the original thread.

Thanks a lot!

-- 
tejun
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