Hi, > > MTU change and set channels operations are implemented as netvsc device > re-creation destroying internal structures (struct net_device stays). This > is really unfortunate but there is no support from Hyper-V host to do it > in a different way. Such re-creation is unsurprisingly racy, Haiyang > reported a crash when netvsc_change_mtu() is racing with > netvsc_link_change() but I was able to identify additional races upon > investigation. Both netvsc_set_channels() and netvsc_change_mtu() race > against: > 1) netvsc_link_change() > 2) netvsc_remove() > 3) netvsc_send() >
after having a look into this driver I got the impression that you are working around an unfortunate implementation of the shutdown sequence in the remove function: If you do unregister_netdev() first instead of resource cleanup then neither set_channels() nor change_mtu() can race with remove(). This is since after unregister_netdev() returns the netdev is not longer available from userspace and thus neither set_channels nor change_mtu can be called anymore (note that all of these functions are protected by the rtnl_lock). To avoid the race between netvsc_change_mtu()/netvsc_set_channels() and netvsc_link_change() you have to stop the concerning worker thread (dwork) before you call netvsc_close() and restart it once the device is up again. Regards, Lino _______________________________________________ devel mailing list de...@linuxdriverproject.org http://driverdev.linuxdriverproject.org/mailman/listinfo/driverdev-devel
