Date: Fri, 14 Dec 2007 16:28:47 +0100 From: Maxime Henrion <mux@FreeBSD.org> To: Stephen Clark <Stephen.Clark@seclark.us> Cc: net@FreeBSD.org Subject: Re: Deadlock in the routing code Message-ID: <20071214152847.GH71713@elvis.mu.org> In-Reply-To: <47617027.3020500@seclark.us> References: <20071213133817.GC71713@elvis.mu.org> <47617027.3020500@seclark.us>
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Stephen Clark wrote: > Maxime Henrion wrote: > > >Replying to myself on this one, sorry about that. > > > >I said in my previous mail that I didn't know yet what process was > >holding the lock of the rtentry that the routed process is dealing > >with in rt_setgate(), and I just could verify that it is held by > >the swi1: net thread. > > > >So, in a nutshell: > > > >- The routed process does its business on the routing socket, that ends up > > calling rt_setgate(). While in rt_setgate() it drops the lock on its > > rtentry in order to call rtalloc1(). At this point, the routed > > process hold the gateway route (rtalloc1() returns it locked), and it > > now tries to re-lock the original rtentry. > >- At the same time, the swi net thread calls arpresolve() which ends up > > calling rt_check(). Then rt_check() locks the rtentry, and tries to > > lock the gateway route. > > > >A classical case of deadlock with mutexes because of different locking > >order. Now, it's not obvious to me how to fix it :-). > > > >Maxime > >_______________________________________________ > >freebsd-net@freebsd.org mailing list > >http://lists.freebsd.org/mailman/listinfo/freebsd-net > >To unsubscribe, send any mail to "freebsd-net-unsubscribe@freebsd.org" > > > > > > > what version of freebsd is this? Oops, forgot that bit of information: RELENG_6 as of a few days ago; it does include jhb@'s last fix in this area, if that's what you've been wondering. Cheers, Maxime
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