netdev - Re: Kernel crash after using new Intel NIC (igb)

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Date:	Fri, 27 May 2011 21:56:59 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Arun Sharma <asharma@...com>
Cc:	David Miller <davem@...emloft.net>,
	Maximilian Engelhardt <maxi@...monizer.de>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	StuStaNet Vorstand <vorstand@...sta.mhn.de>,
	Yann Dupont <Yann.Dupont@...v-nantes.fr>,
	Denys Fedoryshchenko <denys@...p.net.lb>
Subject: Re: Kernel crash after using new Intel NIC (igb)

Le vendredi 27 mai 2011 à 10:52 -0700, Arun Sharma a écrit :
> On 5/26/11 8:27 PM, Eric Dumazet wrote:
> 
> Looks good. Thanks for taking care of this.
> 
> > +static bool atomic_add_unless_return(atomic_t *ptr, int a, int u, int *newv)
> > +{
> > +	int cur, old = atomic_read(ptr);
> > +
> > +	while (old != u) {
> > +		*newv = old + a;
> > +		cur = atomic_cmpxchg(ptr, old, *newv);
> > +		if (cur == old)
> > +			return true;
> > +		old = cur;
> > +	}
> > +	return false;
> > +}
> 
> This looks very similar to atomic_add_unless(). If we had a
> 
> __atomic_add_unless() that returned "old", we could then do:
> 
> atomic_add_unless() { return __atomic_add_unless() != u }
> atomic_add_unless_return() { return __atomic_add_unless() + a}
> 

Sure !

I preferred to not touch lot of files in kernel (atomic_add_unless() is
defined in several files) because its a stable candidate patch (2.6.36+)

So a cleanup patch for 2.6.40+ is certainly doable, do you want to do
this ?

Thanks



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