qemu/1002-io-Yield-rather-than-wait-when-already-in-coroutine.patch

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From 5171f2cd3612ce2772b272e4dd8119fdb0c06124 Mon Sep 17 00:00:00 2001
From: Eric Blake <eblake@redhat.com>
Date: Tue, 5 Sep 2017 14:11:12 -0500
Subject: [PATCH 02/15] io: Yield rather than wait when already in coroutine
The new qio_channel_{read,write}{,v}_all functions are documented
as yielding until data is available. When used on a blocking
channel, this yield is done via qio_channel_wait() which spawns
a nested event loop under the hood (so it is that secondary loop
which yields as needed); but if we are already in a coroutine (at
which point QIO_CHANNEL_ERR_BLOCK is only possible if we are a
non-blocking channel), we want to yield the current coroutine
instead of spawning a nested event loop.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170905191114.5959-2-eblake@redhat.com>
Acked-by: Daniel P. Berrange <berrange@redhat.com>
[commit message updated]
Signed-off-by: Eric Blake <eblake@redhat.com>
---
io/channel.c | 12 ++++++++++--
1 file changed, 10 insertions(+), 2 deletions(-)
diff --git a/io/channel.c b/io/channel.c
index 5e8c2f0a91..9e62794cab 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -105,7 +105,11 @@ int qio_channel_readv_all(QIOChannel *ioc,
ssize_t len;
len = qio_channel_readv(ioc, local_iov, nlocal_iov, errp);
if (len == QIO_CHANNEL_ERR_BLOCK) {
- qio_channel_wait(ioc, G_IO_IN);
+ if (qemu_in_coroutine()) {
+ qio_channel_yield(ioc, G_IO_IN);
+ } else {
+ qio_channel_wait(ioc, G_IO_IN);
+ }
continue;
} else if (len < 0) {
goto cleanup;
@@ -143,7 +147,11 @@ int qio_channel_writev_all(QIOChannel *ioc,
ssize_t len;
len = qio_channel_writev(ioc, local_iov, nlocal_iov, errp);
if (len == QIO_CHANNEL_ERR_BLOCK) {
- qio_channel_wait(ioc, G_IO_OUT);
+ if (qemu_in_coroutine()) {
+ qio_channel_yield(ioc, G_IO_OUT);
+ } else {
+ qio_channel_wait(ioc, G_IO_OUT);
+ }
continue;
}
if (len < 0) {
--
2.13.5