netdev - Re: [PATCH] pkt_sched: fq: do not hold qdisc lock while allocating memory

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Message-Id: <20140308.191032.101129109368547659.davem@davemloft.net>
Date:	Sat, 08 Mar 2014 19:10:32 -0500 (EST)
From:	David Miller <davem@...emloft.net>
To:	eric.dumazet@...il.com
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] pkt_sched: fq: do not hold qdisc lock while allocating
 memory

From: Eric Dumazet <eric.dumazet@...il.com>
Date: Fri, 07 Mar 2014 15:02:42 -0800

> On Fri, 2014-03-07 at 17:04 -0500, David Miller wrote:
> 
>> Eric I think you can simplify things a little further, and in fact I
>> think it makes these functions easier to understand.
>> 
>> The fq_resize() part should just grab the lock around the rehash and
>> the update of q->fq_root and q->fq_trees_log.
>> 
>> fq_change() should only grab the lock around the fq_dequeue() loop
>> and the call to qdisc_tree_descrease_qlen().  The rest of this
>> function is just validating netlink attributes and looking at state
>> that cannot change while we hold RTNL.
> 
> Hmm, but all these parameters we change in fq_change() are read by other
> cpus doing enqueue()/dequeue().
> 
> They are integers, so a race would be not a big deal I guess, but better
> add a fat comment then ;)

Good point, this patch as-is is fine, so applied.
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