netdev - Re: [PATCH net] net: neighbour: add neighbour dead check for neigh_timer

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Message-ID: <1386170645.30495.108.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 04 Dec 2013 07:24:05 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ding Tianhong <dingtianhong@...wei.com>
Cc:	David Miller <davem@...emloft.net>, gaofeng@...fujitsu.com,
	yoshfuji@...ux-ipv6.org, joe@...ches.com, vfalico@...hat.com,
	netdev@...r.kernel.org
Subject: Re: [PATCH net] net: neighbour: add neighbour dead check for
 neigh_timer_handler()

On Wed, 2013-12-04 at 17:16 +0800, Ding Tianhong wrote:
> >> 						base->running_timer = neigh->timer;
> >> 						neigh_timer_handler() => at this time, refcnt is 2;
> >>
> >> user->	neigh_changeaddr()
> >> 	neigh_flush_dev();
> >> 	neigh_del_imer, refcnt dec to 1;
> > 
> > Nope : del_timer() would return 0 here, so we do not decrement refcnt.
> > 
> 
> The first call for del_timer() will return 1, because the timer->entry.next is not NULL,
> then in the neigh_destroy, the del_timer() again will return 0 because timer->entry.next is NULL. 

Again no. You are very mistaken.

del_timer() return code is not a hint. Its a precise meaning.

It cannot return 1 if the timer function is running or is about to run.

If you believe there is  bug in del_timer(), fix it ;)



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