On Fri, Mar 29, 2013 at 8:21 AM, liu ping fan <qemul...@gmail.com> wrote:
> On Thu, Mar 28, 2013 at 10:34 PM, Stefan Hajnoczi <stefa...@gmail.com> wrote:
>> On Thu, Mar 28, 2013 at 03:55:53PM +0800, Liu Ping Fan wrote:
>>> From: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
>>>
>>> Signed-off-by: Liu Ping Fan <pingf...@linux.vnet.ibm.com>
>>> ---
>>> net/tap.c | 7 ++++++-
>>> 1 files changed, 6 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/net/tap.c b/net/tap.c
>>> index 0b663d1..401161c 100644
>>> --- a/net/tap.c
>>> +++ b/net/tap.c
>>> @@ -321,9 +321,14 @@ static void tap_cleanup(NetClientState *nc)
>>> static void tap_poll(NetClientState *nc, bool enable)
>>> {
>>> TAPState *s = DO_UPCAST(TAPState, nc, nc);
>>> - /* fixme, when tap backend on another thread, the disable should be
>>> sync */
>>> +
>>> tap_read_poll(s, enable);
>>> tap_write_poll(s, enable);
>>> +
>>> + if (!enable) {
>>> + /* need sync so vhost can take over polling */
>>> + g_source_remove_poll(&nc->nsrc->source, &nc->nsrc->gfd);
>>> + }
>>
>> Is this necessary?
>>
>> Since we're in tap_poll() we are currently not in poll(2) waiting on the
>> fd. Therefore it's safe for the caller to use the fd, the prepare
>> function will remove it from the fd set before glib calls poll(2) again.
>>
> The main purpose is to make sure that the GSource->dispatch is not
> in-flight, in which case, both vhost handler and ->dispatch() will
> work on it.
Okay, I see. hw/vhost_net.c will give the fd to the vhost kernel
module. We need to be sure the fd is no longer in use - and we don't
want tap readable/writable handlers to be called.
Stefan
