Re: [PATCH] ipv4 : igmp : optimize timer modify logic in igmp_mod_timer()
From: Eric Dumazet <hidden>
Date: 2011-11-23 15:42:50
Le mercredi 23 novembre 2011 à 23:26 +0800, Jun Zhao a écrit :
quoted hunk ↗ jump to hunk
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 <redacted> --- 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 ?
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.