On 05.08.2013 16:59, Bryan Venteicher wrote:
----- 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?).
Yes. I have received a grant from the FF to look at this in depth,
evaluate different approaches and to propose an implementation for
the whole stack.
--
Andre
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
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