Re: [Qemu-devel] [PATCH] timer: fix qemu_poll_ns early timeout on windows

[Stefan Weil]

Am 18.04.2014 09:34, schrieb Stanislav Vorobiov:
> Hi,
> 
> Please see below
> 
> On 04/18/2014 10:46 AM, Stefan Weil wrote:
>> Hi,
[...]
> 
>>
>> Would it be sufficient to round any timeout > 0 and < 10 to 10 for
>> Windows hosts? Maybe this could be done in qemu_timeout_ns_to_ms.
> We tried that, it gets almost as good as with this patch, but this
> makes timeouts like, say, 2ms wait for 10ms, so with this patch it's
> still better.
> 
>> If
>> this does not work, we still can use g_poll for timeout >= 10 and call a
>> new Windows specific polling function for timeout < 10.
> Does it have a point to separate things, if we've implemented this for 
> timeouts < 10ms
> why not use it for timeouts >= 10ms ? The code in this patch is in fact 
> g_poll's
> implementation without that "timeout >= 10" hack and it handles timeouts >= 
> 10ms
> as well as g_poll does.


Did you send a bug report to the maintainers of glib? I think it would
be good to do so.

We can override the buggy implementation of g_poll for Windows by
redirecting any call of g_poll to a new g_poll_fixed function.

In file include/glib-compat.h:

#if defined(_WIN32)
/* g_poll does not handle timeout < 10 ms correctly, so use wrapper. */
#define g_poll(fds, nfds, timeout) g_poll_fixed((fds, nfds, timeout)
gint g_poll_fixed(GPollFD *fds, guint nfds, gint timeout);
#endif

Then move your code into a new function g_poll_fixed() in file
util/oslib-win32.c (and add there some comments, too).

There is also some g_poll code in include/qemu-common.h. This should
also be moved to include/glib-compat.h and must be excluded for _WIN32
when you add g_poll_fixed.

Stefan