netdev - Re: [PATCH net-next-2.6 v2] pkt_sched: gen_estimator: kill est

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Message-ID: <4C0E9A2E.9080109@gmail.com>
Date:	Tue, 08 Jun 2010 21:29:50 +0200
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Changli Gao <xiaosuo@...il.com>,
	David Miller <davem@...emloft.net>,
	netdev <netdev@...r.kernel.org>,
	Stephen Hemminger <shemminger@...tta.com>,
	Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH net-next-2.6 v2] pkt_sched: gen_estimator: kill est_lock
 rwlock

Jarek Poplawski wrote, On 06/08/2010 02:40 PM:

> On Tue, Jun 08, 2010 at 02:27:32PM +0200, Eric Dumazet wrote:
>> Le mardi 08 juin 2010 ?? 12:15 +0000, Jarek Poplawski a écrit :
>>
>>> Actually, I guess, Changli meant the bug introduced by your previous
>>> patch by removing the est_lock. With this lock (and your commit 5d944)
>>> bstats (and API) seem "fundamentaly" safe.
>>>
>> Sorry, I have no idea of what you want to say, I cant find commit 5d944.
>>
> 
> Sorry, I meant the commit mentioned in your changelog which was quoted.
> 
>> This was partially addressed in commit 5d944c640b4 (gen_estimator:
>> deadlock fix), but same problem exist for all gen_kill_estimator()
>> users.

In case it's still unclear, I wanted to say that IMHO this patch's
title and changelog are misleading because most of its content are
est_lock to RCU changes - not fixes.

>> [PATCH net-next-2.6] pkt_sched: gen_kill_estimator() rcu fixes
>> 
>> gen_kill_estimator() API is fundamentaly wrong, since caller should make
>> sure an RCU grace period is respected before freeing bstats or lock.

Freeing bstats doesn't currently require RCU protection.

Jarek P.
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