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Re: [Qemu-devel] [RFC PATCH v2 2/4] net: resolve race of tap backend and
From: |
liu ping fan |
Subject: |
Re: [Qemu-devel] [RFC PATCH v2 2/4] net: resolve race of tap backend and its peer |
Date: |
Fri, 29 Mar 2013 15:21:29 +0800 |
On Thu, Mar 28, 2013 at 10:34 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Thu, Mar 28, 2013 at 03:55:53PM +0800, Liu Ping Fan wrote:
>> From: Liu Ping Fan <address@hidden>
>>
>> Signed-off-by: Liu Ping Fan <address@hidden>
>> ---
>> 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.
Regards
Pingfan
> Stefan
- [Qemu-devel] [RFC PATCH v2 0/4] port network layer onto glib, Liu Ping Fan, 2013/03/28
- [Qemu-devel] [RFC PATCH v2 3/4] net: port hub onto glib, Liu Ping Fan, 2013/03/28
- [Qemu-devel] [RFC PATCH v2 4/4] net: port virtio net onto glib, Liu Ping Fan, 2013/03/28
- Re: [Qemu-devel] [RFC PATCH v2 0/4] port network layer onto glib, Paolo Bonzini, 2013/03/28
- Re: [Qemu-devel] [RFC PATCH v2 0/4] port network layer onto glib, Stefan Hajnoczi, 2013/03/28