netdev - Re: [PATCH] IPV4 : Move ip route cache flush (secret

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Message-Id: <20071117.181313.217111568.davem@davemloft.net>
Date:	Sat, 17 Nov 2007 18:13:13 -0800 (PST)
From:	David Miller <davem@...emloft.net>
To:	herbert@...dor.apana.org.au
Cc:	dada1@...mosbay.com, netdev@...r.kernel.org
Subject: Re: [PATCH] IPV4 : Move ip route cache flush (secret_rebuild) from
 softirq to workqueue

From: Herbert Xu <herbert@...dor.apana.org.au>
Date: Sun, 18 Nov 2007 10:07:37 +0800

> On Sat, Nov 17, 2007 at 04:45:42PM -0800, David Miller wrote:
> >
> > Herbert, you asked about just nop'ing out cond_resched() when we're
> > doing real preemption.
> > 
> > A lot of code goes:
> > 
> > 	if (need_resched()) {
> > 		/* drop some locks, etc. */
> > 		cond_resched();
> > 		/* reacquire locks, etc. */
> > 	}
> > 
> > So it has to do something even with real preemption enabled.
> 
> Actually that shouldn't be necessary.  Because things like spin_unlock
> does preempt_enable which in turn does:
> 
> #define preempt_enable() \
> do { \
>         preempt_enable_no_resched(); \
>         barrier(); \
>         preempt_check_resched(); \
> } while (0)
> 
> when CONFIG_PREEMPT is enabled.  So at least in this case the
> cond_resched call is superfluous.

I see what you mean, ok yes that would catch it.
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