Date: Mon, 5 Aug 2013 09:59:32 -0500 (CDT) From: Bryan Venteicher <bryanv@daemoninthecloset.org> To: Luigi Rizzo <rizzo@iet.unipi.it> Cc: current@freebsd.org, net@freebsd.org Subject: Re: [net] protecting interfaces from races between control and data ? Message-ID: <2034715395.855.1375714772487.JavaMail.root@daemoninthecloset.org> In-Reply-To: <20130805082307.GA35162@onelab2.iet.unipi.it> References: <20130805082307.GA35162@onelab2.iet.unipi.it>
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----- Original Message ----- > i am slightly unclear of what mechanisms we use to prevent races > between interface being reconfigured (up/down/multicast setting, etc, > all causing reinitialization of the rx and tx rings) and > > i) packets from the host stack being sent out; > ii) interrupts from the network card being processed. > > I think in the old times IFF_DRV_RUNNING was used for this purpose, > but now it is not enough. > Acquiring the "core lock" in the NIC does not seem enough, either, > because newer drivers, especially multiqueue ones, have per-queue > rx and tx locks. > What I've done in my drivers is: * Lock the core mutex * Clear IFF_DRV_RUNNING * Lock/unlock each queue's lock The various Rx/Tx queue functions check for IFF_DRV_RUNNING after (re)acquiring their queue lock. See at vtnet_stop_rendezvous() at [1] for an example. > Does anyone know if there is a generic mechanism, or each driver > reimplements its own way ? > We desperately need a saner ifnet/driver interface. I think andre@ had some previous work in this area (and additional plans as well?). IMO, there's a lot to like on what DragonflyBSD has done in this area. [1] - http://svnweb.freebsd.org/base/user/bryanv/vtnetmq/sys/dev/virtio/network/if_vtnet.c?revision=252451&view=markup > thanks > luigi > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org" >
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