netdev - Re: [PATCH 2/2] udp: RCU handling for Unicast packets.

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Message-ID: <49099A8C.8030709@cosmosbay.com>
Date:	Thu, 30 Oct 2008 12:29:16 +0100
From:	Eric Dumazet <dada1@...mosbay.com>
To:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Corey Minyard <minyard@....org>,
	David Miller <davem@...emloft.net>, shemminger@...tta.com,
	benny+usenet@...rsen.dk, netdev@...r.kernel.org,
	paulmck@...ux.vnet.ibm.com,
	Christoph Lameter <cl@...ux-foundation.org>,
	johnpol@....mipt.ru, Christian Bell <christian@...i.com>
Subject: Re: [PATCH 2/2] udp: RCU handling for Unicast packets.

Peter Zijlstra a écrit :
> On Wed, 2008-10-29 at 15:36 +0100, Eric Dumazet wrote:
>> +/**
>> + * hlist_for_each_entry_rcu_safenext - iterate over rcu list of given type
>> + * @tpos:      the type * to use as a loop cursor.
>> + * @pos:       the &struct hlist_node to use as a loop cursor.
>> + * @head:      the head for your list.
>> + * @member:    the name of the hlist_node within the struct.
>> + * @next:       the &struct hlist_node to use as a next cursor
>> + *
>> + * Special version of hlist_for_each_entry_rcu that make sure
>> + * each next pointer is fetched before each iteration.
>> + */
>> +#define hlist_for_each_entry_rcu_safenext(tpos, pos, head, member, next) \
>> +       for (pos = rcu_dereference((head)->first);                       \
>> +               pos && ({ next = pos->next; smp_rmb(); prefetch(next); 1; }) && \
>> +               ({ tpos = hlist_entry(pos, typeof(*tpos), member); 1; }); \
>> +               pos = rcu_dereference(next))
>> +
> 
> why _safenext and not _safe like hlist_for_each_entry_safe() which also
> keeps a next pointer?
> 
> Also note the difference in argument order between these two.
> 

Yes, this one is going to vanish soon.


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