Re: [Qemu-devel] [PATCH 10/10] aio-win32: add support for sockets

[TeLeMan]

On Fri, Sep 12, 2014 at 6:05 PM, Paolo Bonzini <address@hidden> wrote:
> Il 12/09/2014 03:39, TeLeMan ha scritto:
>> On Wed, Jul 9, 2014 at 5:53 PM, Paolo Bonzini <address@hidden> wrote:
>>> diff --git a/aio-win32.c b/aio-win32.c
>>> index 4542270..61e3d2d 100644
>>> --- a/aio-win32.c
>>> +++ b/aio-win32.c
>>> +    bool was_dispatching, progress, have_select_revents, first;
>> have_select_revents has no initial value.
>
> Good catch here...
>
>>
>>> @@ -183,6 +318,7 @@ bool aio_poll(AioContext *ctx, bool blocking)
>>>
>>>      /* wait until next event */
>>>      while (count > 0) {
>>> +        HANDLE event;
>>>          int ret;
>>>
>>>          timeout = blocking
>>> @@ -196,13 +332,17 @@ bool aio_poll(AioContext *ctx, bool blocking)
>>>          first = false;
>>>
>>>          /* if we have any signaled events, dispatch event */
>>> -        if ((DWORD) (ret - WAIT_OBJECT_0) >= count) {
>>> +        event = NULL;
>>> +        if ((DWORD) (ret - WAIT_OBJECT_0) < count) {
>>> +            event = events[ret - WAIT_OBJECT_0];
>>> +        } else if (!have_select_revents) {
>>
>> when (ret - WAIT_OBJECT_0) >= count and have_select_revents is true,
>> the following events[ret - WAIT_OBJECT_0] will be overflowed.
>
> ... this instead is not a problem, ret - WAIT_OBJECT_0 can be at most
> equal to count, and events[] is declared with MAXIMUM_WAIT_OBJECTS + 1
> places.  So the
>
>         events[ret - WAIT_OBJECT_0] = events[--count];
>
> is equal to
>
>         events[count] = events[count - 1];
>         --count;
>
> and this is harmless.

WAIT_ABANDONED_0 & WAIT_TIMEOUT & WAIT_FAILED are larger than
MAXIMUM_WAIT_OBJECTS.

> Paolo
>
>>>              break;
>>>          }
>>>
>>> +        have_select_revents = false;
>>>          blocking = false;
>>>
>>> -        progress |= aio_dispatch_handlers(ctx, events[ret - 
>>> WAIT_OBJECT_0]);
>>> +        progress |= aio_dispatch_handlers(ctx, event);
>>>
>>>          /* Try again, but only call each handler once.  */
>>>          events[ret - WAIT_OBJECT_0] = events[--count];
>