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Re: [Qemu-devel] [PATCH 03/20] char: add IOWatchPoll support
From: |
Anthony Liguori |
Subject: |
Re: [Qemu-devel] [PATCH 03/20] char: add IOWatchPoll support |
Date: |
Fri, 29 Mar 2013 09:03:10 -0500 |
User-agent: |
Notmuch/0.13.2+93~ged93d79 (http://notmuchmail.org) Emacs/23.3.1 (x86_64-pc-linux-gnu) |
Amit Shah <address@hidden> writes:
> On (Fri) 29 Mar 2013 [07:24:07], Anthony Liguori wrote:
>> Amit Shah <address@hidden> writes:
>>
>> > On (Tue) 05 Mar 2013 [23:21:18], Amit Shah wrote:
>> >> From: Anthony Liguori <address@hidden>
>> >>
>> >> This is a special GSource that supports CharDriverState style
>> >> poll callbacks.
>> >>
>> >> For reviewability and bisectability, this code is #if 0'd out in this
>> >> patch to avoid unused warnings since all of the functions are static.
>> >>
>> >> Signed-off-by: Anthony Liguori <address@hidden>
>> >> Signed-off-by: Amit Shah <address@hidden>
>> >
>> >
>> >> +static int io_channel_send_all(GIOChannel *fd, const void *_buf, int
>> >> len1)
>> >> +{
>> >> + GIOStatus status;
>> >> + gsize bytes_written;
>> >> + int len;
>> >> + const uint8_t *buf = _buf;
>> >> +
>> >> + len = len1;
>> >> + while (len > 0) {
>> >> + status = g_io_channel_write_chars(fd, (const gchar *)buf, len,
>> >> + &bytes_written, NULL);
>> >> + if (status != G_IO_STATUS_NORMAL) {
>> >> + if (status != G_IO_STATUS_AGAIN) {
>> >> + return -1;
>> >> + }
>> >
>> > It's not quite right to return -1 here; previous iterations of the
>> > while loop could have successfully written data, and (len1 - len)
>> > could be +ve.
>>
>> Once -1 is returned, it's a terminal error. It doesn't matter that we
>> may have written some data.
>
> Why do you say that?
Because you're quoting the wrong patch :-) This bit is rewritten by a
later patch which is the source of your problem below. In the patch you
quote, we busy spin until all data is written. However, with:
commit 23673ca740e0eda66901ca801a5a901df378b063
Author: Anthony Liguori <address@hidden>
Date: Tue Mar 5 23:21:23 2013 +0530
qemu-char: add watch support
We started to return EAGAIN even if we have a partially successful
write. I'm running a patch through testing right now that rewrites this
function to have sane semantics (return bytes written on partial write).
I'll post as soon as testing completes.
Regards,
Anthony Liguori
[Qemu-devel] [PATCH 04/20] qemu-char: convert fd_chr to use a GIOChannel, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 05/20] qemu-char: convert pty to GIOChannel, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 06/20] qemu-char: convert UDP to GIOChannel, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 07/20] qemu-char: tcp: make use GIOChannel, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 08/20] qemu-char: add watch support, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 09/20] qemu-char: add pty watch, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 10/20] char: add gio watch fn for tcp backends, Amit Shah, 2013/03/05
[Qemu-devel] [PATCH 11/20] qemu-char: use a glib timeout instead of qemu-timer, Amit Shah, 2013/03/05