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Re: [Qemu-devel] [PATCH v1 1/1] io/channel-watch.c: Only select on what
From: |
Daniel P. Berrange |
Subject: |
Re: [Qemu-devel] [PATCH v1 1/1] io/channel-watch.c: Only select on what we are actually waiting for |
Date: |
Thu, 13 Jul 2017 11:23:59 +0100 |
User-agent: |
Mutt/1.8.3 (2017-05-23) |
On Thu, Jul 13, 2017 at 03:15:49AM -0700, Alistair Francis wrote:
> When calling WAEventSelect() only wait on events as specified by the
> condition variable. This requires that the condition variable is set
> correctly for the specific events that we need to wait for.
Can you describe the actual problem / buggy behaviour you were seeing
with the current code.
> Signed-off-by: Alistair Francis <address@hidden>
> ---
>
> io/channel-watch.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/io/channel-watch.c b/io/channel-watch.c
> index 8640d1c464..d80722f496 100644
> --- a/io/channel-watch.c
> +++ b/io/channel-watch.c
> @@ -286,9 +286,21 @@ GSource *qio_channel_create_socket_watch(QIOChannel *ioc,
> QIOChannelSocketSource *ssource;
>
> #ifdef WIN32
> - WSAEventSelect(socket, ioc->event,
> - FD_READ | FD_ACCEPT | FD_CLOSE |
> - FD_CONNECT | FD_WRITE | FD_OOB);
> + long bitmask = 0;
> +
> + if (condition & (G_IO_IN | G_IO_PRI)) {
> + bitmask |= FD_READ | FD_ACCEPT;
> + }
> +
> + if (condition & G_IO_HUP) {
> + bitmask |= FD_CLOSE;
> + }
> +
> + if (condition & G_IO_OUT) {
> + bitmask |= FD_WRITE | FD_CONNECT;
> + }
> +
> + WSAEventSelect(socket, ioc->event, bitmask);
> #endif
I think the problem with doing this is that WSAEventSelect is a global
setting that applies to the socket handle. If you use qio_channel_create_watch
twice on the same socket with different events, the second watch will break
the first watch by potentially discarding events that it requested.
Regards,
Daniel
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