Re: [Qemu-devel] [RFC PATCH v4 04/15] net: resolve race of tap backend and its peer

[liu ping fan]

On Thu, Apr 18, 2013 at 10:11 PM, Stefan Hajnoczi <address@hidden> wrote:
> On Wed, Apr 17, 2013 at 04:39:13PM +0800, Liu Ping Fan wrote:
>> From: Liu Ping Fan <address@hidden>
>>
>> When vhost net enabled, we should be sure that the user space
>> fd handler is not in flight
>>
>> Signed-off-by: Liu Ping Fan <address@hidden>
>> ---
>>  net/tap.c |    5 +++++
>>  1 files changed, 5 insertions(+), 0 deletions(-)
>>
>> diff --git a/net/tap.c b/net/tap.c
>> index 35cbb6e..b5629e3 100644
>> --- a/net/tap.c
>> +++ b/net/tap.c
>> @@ -41,6 +41,7 @@
>>  #include "qemu/error-report.h"
>>
>>  #include "net/tap.h"
>> +#include "util/event_gsource.h"
>>
>>  #include "hw/vhost_net.h"
>>
>> @@ -327,6 +328,10 @@ static void tap_poll(NetClientState *nc, bool enable)
>>      tap_read_poll(s, enable);
>>      tap_write_poll(s, enable);
>>
>> +    if (!enable) {
>> +        /* need sync so vhost can take over polling */
>> +        g_source_remove_poll(&s->nsrc->source, &s->nsrc->gfd);
>> +    }
>
> We must also re-enable it when .poll(nc, true) is called.
>
Yes, will fix it.

> Please drop the comments the previous patch added.  In fact, this patch
> can be squashed.
>
Ok.
> I think there was another vhost sync comment which you haven't addressed
> here.  See the previous patch.
>
It is related with multi-queue, and I check the code, it can be async.
 I will drop the related comment in previous patch

Thanks, Pingfan

> Stefan