Messages in this thread | | | Subject | Re: [PATCH net] tuntap: raise EPOLLOUT on device up | From | Jason Wang <> | Date | Fri, 18 May 2018 22:00:31 +0800 |
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On 2018年05月18日 21:26, Jason Wang wrote: > > > On 2018年05月18日 21:13, Michael S. Tsirkin wrote: >> On Fri, May 18, 2018 at 09:00:43PM +0800, Jason Wang wrote: >>> We return -EIO on device down but can not raise EPOLLOUT after it was >>> up. This may confuse user like vhost which expects tuntap to raise >>> EPOLLOUT to re-enable its TX routine after tuntap is down. This could >>> be easily reproduced by transmitting packets from VM while down and up >>> the tap device. Fixing this by set SOCKWQ_ASYNC_NOSPACE on -EIO. >>> >>> Cc: Hannes Frederic Sowa <hannes@stressinduktion.org> >>> Cc: Eric Dumazet <edumazet@google.com> >>> Fixes: 1bd4978a88ac2 ("tun: honor IFF_UP in tun_get_user()") >>> Signed-off-by: Jason Wang <jasowang@redhat.com> >>> --- >>> drivers/net/tun.c | 4 +++- >>> 1 file changed, 3 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c >>> index d45ac37..1b29761 100644 >>> --- a/drivers/net/tun.c >>> +++ b/drivers/net/tun.c >>> @@ -1734,8 +1734,10 @@ static ssize_t tun_get_user(struct tun_struct >>> *tun, struct tun_file *tfile, >>> int skb_xdp = 1; >>> bool frags = tun_napi_frags_enabled(tun); >>> - if (!(tun->dev->flags & IFF_UP)) >>> + if (!(tun->dev->flags & IFF_UP)) { >> Isn't this racy? What if flag is cleared at this point? > > I think you mean "set at this point"? Then yes, so we probably need to > set the bit during tun_net_close(). > > Thanks
Looks no need, vhost will poll socket after it see EIO. So we are ok here?
Thanks
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