From: Eric Blake Date: Tue, 5 Sep 2017 14:11:12 -0500 Subject: [PATCH] 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 Message-Id: <20170905191114.5959-2-eblake@redhat.com> Acked-by: Daniel P. Berrange [commit message updated] Signed-off-by: Eric Blake --- 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) {