Commit 9ffb8270 authored Sep 05, 2017 by Eric Blake

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>

parent 3f5c4076

io/channel.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -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) {
		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) {
		if (qemu_in_coroutine()) {
		qio_channel_yield(ioc, G_IO_OUT);
		} else {
		qio_channel_wait(ioc, G_IO_OUT);
		}
		continue;
		}
		if (len < 0) {