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Message-ID: <1322063076.6253.1.camel@barry.pixelworks.com>
Date: Wed, 23 Nov 2011 23:44:36 +0800
From: Jun Zhao <mypopydev@...il.com>
To: Eric Dumazet <eric.dumazet@...il.com>
Cc: davem@...emloft.net, netdev@...r.kernel.org
Subject: Re: [PATCH] ipv4 : igmp : optimize timer modify logic in
igmp_mod_timer()
On Wed, 2011-11-23 at 16:42 +0100, Eric Dumazet wrote:
> Le mercredi 23 novembre 2011 à 23:26 +0800, Jun Zhao a écrit :
> > When timer is pending and expires less-than-or-equal-to new delay,
> > we need not used del_timer()/add_timer().
> >
> > Signed-off-by: Jun Zhao <mypopydev@...il.com>
> > ---
> > net/ipv4/igmp.c | 12 ++++++------
> > 1 files changed, 6 insertions(+), 6 deletions(-)
> >
> > diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
> > index c7472ef..50d06c5 100644
> > --- a/net/ipv4/igmp.c
> > +++ b/net/ipv4/igmp.c
> > @@ -215,14 +215,14 @@ static void igmp_mod_timer(struct ip_mc_list *im, int max_delay)
> > {
> > spin_lock_bh(&im->lock);
> > im->unsolicit_count = 0;
> > - if (del_timer(&im->timer)) {
> > - if ((long)(im->timer.expires-jiffies) < max_delay) {
> > - add_timer(&im->timer);
> > - im->tm_running = 1;
> > - spin_unlock_bh(&im->lock);
> > + if (timer_pending(&im->timer)) {
> > + if (time_before_eq(im->timer.expires, (jiffies + max_delay))) {
> > + spin_lock_bh(&im->lock);
>
> And you actually tested this patch ?
Sorry for this mistake. :(. spin_lock_bh -> spin_unlock_bh
>
> > return;
> > + } else {
> > + del_timer(&im->timer);
> > + atomic_dec(&im->refcnt);
> > }
> > - atomic_dec(&im->refcnt);
> > }
> > igmp_start_timer(im, max_delay);
> > spin_unlock_bh(&im->lock);
>
>
> Not sure why you want to optimize this very rare function call, risking
> adding bugs in it.
>
>
>
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