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Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 u
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select |
Date: |
Wed, 9 Mar 2016 18:47:29 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.6.0 |
On 09/03/2016 18:28, Daniel P. Berrange wrote:
> From: Paolo Bonzini <address@hidden>
Reviewing my own patch looks weird. :)
> On Win32 we cannot directly poll on socket handles. Instead we
> create a Win32 event object and associate the socket handle with
> the event. When the event signals readyness we then have to
> use select to determine which events are ready. Creating Win32
> events is moderately heavyweight, so we don't want todo it
> every time we create a GSource, so this associates a single
> event with a QIOChannel.
>
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
> include/io/channel.h | 3 ++
> io/channel-socket.c | 9 ++++
> io/channel-watch.c | 136
> ++++++++++++++++++++++++++++++++++++++++++++++++++-
> io/channel.c | 14 ++++++
> 4 files changed, 161 insertions(+), 1 deletion(-)
>
> diff --git a/include/io/channel.h b/include/io/channel.h
> index 0a1f1ce..20b973a 100644
> --- a/include/io/channel.h
> +++ b/include/io/channel.h
> @@ -78,6 +78,9 @@ typedef gboolean (*QIOChannelFunc)(QIOChannel *ioc,
> struct QIOChannel {
> Object parent;
> unsigned int features; /* bitmask of QIOChannelFeatures */
> +#ifdef _WIN32
> + HANDLE event; /* For use with GSource on Win23 */
Even s390 would have Win24 and Win31 but not Win23. :)
> +#endif
> };
>
> /**
> diff --git a/io/channel-socket.c b/io/channel-socket.c
> index 6f7f594..ff49853 100644
> --- a/io/channel-socket.c
> +++ b/io/channel-socket.c
> @@ -55,6 +55,10 @@ qio_channel_socket_new(void)
> ioc = QIO_CHANNEL(sioc);
> ioc->features |= (1 << QIO_CHANNEL_FEATURE_SHUTDOWN);
>
> +#ifdef WIN32
> + ioc->event = CreateEvent(NULL, FALSE, FALSE, NULL);
> +#endif
> +
> trace_qio_channel_socket_new(sioc);
>
> return sioc;
> @@ -341,6 +345,11 @@ qio_channel_socket_accept(QIOChannelSocket *ioc,
> cioc->remoteAddrLen = sizeof(ioc->remoteAddr);
> cioc->localAddrLen = sizeof(ioc->localAddr);
>
> +#ifdef WIN32
> + ((QIOChannel *)cioc)->event = CreateEvent(NULL, FALSE, FALSE, NULL);
> +#endif
QIO_CHANNEL(cioc)->event?
> + WSAEventSelect(ssource->socket, NULL, 0);
This should probably be moved in qio_channel_socket_finalize.
>
> + /* WSAEnumNetworkEvents is edge-triggered, so we need a separate
> + * call to select to find which events are actually available.
> + * However, if there were no reported events at the time of the last
> + * call, and no new events since then, we know that the socket is
> + * quiescent.
> + */
> + if (!ssource->revents && !ev.lNetworkEvents) {
> + return 0;
> + }
> +
This is unfortunately unsafe, because:
1) WSAEventSelect clears all pending events (so the next
WSAEnumNetworkEvents returns no FD_READ, unless you have read all data
in the buffer with recv)
2) setting a socket to non-blocking should call WSAEventSelect (see
below), but cannot e.g. set ->revents to ~0 for all existing GSource.
It's probably possible to add a generation count or something like that,
but for now please revert this part (I had made it a separate commit in
my prototype because I wasn't sure if it was okay).
> + ssource->condition = condition;
> + ssource->socket = socket;
> + ssource->revents = 0;
> + ssource->fd.fd = (gintptr)ioc->event;
> + ssource->fd.events = G_IO_IN;
> +
> + g_source_add_poll(source, &ssource->fd);
> + WSAEventSelect(ssource->socket, ioc->event,
> + FD_READ | FD_ACCEPT | FD_CLOSE |
> + FD_CONNECT | FD_WRITE | FD_OOB);
This should be moved where the socket is made non-blocking in
qio_channel_socket_set_blocking (because qemu_qemu_set_nonblock also
calls WSAEventSelect).
It's probably worth adding a comment that
qio_channel_socket_source_check only works in non-blocking mode for Windows.
Thanks,
Paolo
- Re: [Qemu-devel] [PATCH v1 01/21] osdep: fix socket_error() to work with Mingw64, (continued)
- [Qemu-devel] [PATCH v1 04/21] io: bind to socket before creating QIOChannelSocket, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 05/21] io: wait for incoming client in socket test, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 06/21] io: set correct error object in background reader test thread, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 07/21] io: assert errors before asserting content in I/O test, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 08/21] io: fix copy+paste mistake in socket error message, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 09/21] io: add missing EWOULDBLOCK checks in Win32 I/O code paths, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 10/21] io: pass HANDLE to g_source_add_poll on Win32, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 11/21] io: introduce qio_channel_create_socket_watch, Daniel P. Berrange, 2016/03/09
- [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Daniel P. Berrange, 2016/03/09
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select,
Paolo Bonzini <=
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Eric Blake, 2016/03/09
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Paolo Bonzini, 2016/03/09
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Daniel P. Berrange, 2016/03/10
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Paolo Bonzini, 2016/03/10
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Eric Blake, 2016/03/10
- Re: [Qemu-devel] [PATCH v1 12/21] io: implement socket watch for win32 using WSAEventSelect+select, Daniel P. Berrange, 2016/03/10
[Qemu-devel] [PATCH v1 14/21] char: remove qemu_chr_finish_socket_connection method, Daniel P. Berrange, 2016/03/09
[Qemu-devel] [PATCH v1 13/21] char: ensure listener socket is in blocking mode when waiting, Daniel P. Berrange, 2016/03/09