[libvirt] mingw: virsh event loop failure in current git

[Daniel P. Berrange]

On Tue, Mar 15, 2011 at 09:29:14AM +0100, Matthias Bolte wrote:
> Commit 2ed6cc7bec41dd344d41ea1531f6760c93099128 "Expose event loop
> implementation as a public API" turned a failure to initialize the
> default event loop into a fatal error in virsh on Windows. Before that
> commit such a failure was ignored.
> 
> virEventRegisterDefaultImpl calls virEventPollInit that calls
> virSetNonBlock that calls ioctl that is replaced by gnulib and calls
> ioctlsocket. ioctlsocket fails because the given FD is a pipe but
> ioctlsocket expects a socket.

Hmm, isn't this actually a bug in gnulib's ioctl replacement then ?
The goal of gnulib is that you never use a SOCKET in any of the
POSIX APIs it wraps. It hides the WinSock horribleness so that you
can just use normal FDs everywhere.

> A version that works on pipes on Windows looks like this. Although the
> pipe is actually not a named pipe the call to SetNamedPipeHandleState
> doesn't fail at least.
> 
> int
> virSetPipeNonBlock(int fd)
> {
>     DWORD mode = PIPE_NOWAIT;
>     HANDLE handle = _get_osfhandle(fd)
>     BOOL result = SetNamedPipeHandleState(handle, &mode, NULL, NULL);
> 
>     return result ? 0 : -1;
> }
> 
> So, is the event loop stuff supposed to work on Windows at all and we
> should get it fixed? Or do we just put an #ifndef WIN32 around
> virEventRegisterDefaultImpl in virsh, because the only event loop user
> in virsh is the console command that is disabled on Windows anyway?

There were several reasons the console stuff used to be disabled

 - It relied on opening /dev/pts/XXX which obviously only
   makes sense for local connection, not remote ones.
 - It uses the terminal attribute APIs to put the console
   into raw mode.

The event loop is intended to be portable, and certainly, now it is
a public API we should make it work. The opening of /dev/pts/XXX is
no longer a blocker for virsh console on Win32, since we access the
console via the streams APIs. So if we can figure out what todo with
the terminal attribute APIs,  virsh console should work on Win32 (or
any other platform). This is one of the nice benefits of the streams
API

Regards,
Daniel
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