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From 280e240cfa8e633dd062791b1d0d62fe0e642d46 Mon Sep 17 00:00:00 2001
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From: Paolo Bonzini <pbonzini@redhat.com>
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Date: Sat, 2 Dec 2017 12:19:38 +0100
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Subject: [PATCH 12/36] io: Yield rather than wait when already in coroutine
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RH-Author: Paolo Bonzini <pbonzini@redhat.com>
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Message-id: <20171202121953.13317-3-pbonzini@redhat.com>
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Patchwork-id: 78076
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O-Subject: [RHEL7.4 qemu-kvm-rhev PATCH 02/17] io: Yield rather than wait when already in coroutine
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Bugzilla: 1464908
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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From: Eric Blake <eblake@redhat.com>
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The new qio_channel_{read,write}{,v}_all functions are documented
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as yielding until data is available. When used on a blocking
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channel, this yield is done via qio_channel_wait() which spawns
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a nested event loop under the hood (so it is that secondary loop
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which yields as needed); but if we are already in a coroutine (at
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which point QIO_CHANNEL_ERR_BLOCK is only possible if we are a
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non-blocking channel), we want to yield the current coroutine
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instead of spawning a nested event loop.
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Signed-off-by: Eric Blake <eblake@redhat.com>
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Message-Id: <20170905191114.5959-2-eblake@redhat.com>
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Acked-by: Daniel P. Berrange <berrange@redhat.com>
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[commit message updated]
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Signed-off-by: Eric Blake <eblake@redhat.com>
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(cherry picked from commit 9ffb8270205a274a18ee4f8a735e2fccaf957246)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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io/channel.c | 12 ++++++++++--
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1 file changed, 10 insertions(+), 2 deletions(-)
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diff --git a/io/channel.c b/io/channel.c
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index 5e8c2f0..9e62794 100644
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--- a/io/channel.c
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+++ b/io/channel.c
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@@ -105,7 +105,11 @@ int qio_channel_readv_all(QIOChannel *ioc,
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ssize_t len;
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len = qio_channel_readv(ioc, local_iov, nlocal_iov, errp);
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if (len == QIO_CHANNEL_ERR_BLOCK) {
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- qio_channel_wait(ioc, G_IO_IN);
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+ if (qemu_in_coroutine()) {
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+ qio_channel_yield(ioc, G_IO_IN);
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+ } else {
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+ qio_channel_wait(ioc, G_IO_IN);
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+ }
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continue;
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} else if (len < 0) {
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goto cleanup;
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@@ -143,7 +147,11 @@ int qio_channel_writev_all(QIOChannel *ioc,
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ssize_t len;
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len = qio_channel_writev(ioc, local_iov, nlocal_iov, errp);
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if (len == QIO_CHANNEL_ERR_BLOCK) {
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- qio_channel_wait(ioc, G_IO_OUT);
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+ if (qemu_in_coroutine()) {
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+ qio_channel_yield(ioc, G_IO_OUT);
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+ } else {
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+ qio_channel_wait(ioc, G_IO_OUT);
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+ }
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continue;
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}
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if (len < 0) {
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--
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1.8.3.1
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