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

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Message-ID: <20071118020737.GA24821@gondor.apana.org.au>
Date:	Sun, 18 Nov 2007 10:07:37 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	dada1@...mosbay.com, netdev@...r.kernel.org
Subject: Re: [PATCH] IPV4 : Move ip route cache flush (secret_rebuild) from softirq to workqueue

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.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
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