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

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Message-ID: <1394233362.20149.47.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Fri, 07 Mar 2014 15:02:42 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH] pkt_sched: fq: do not hold qdisc lock while allocating
 memory

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 ;)


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