[Qemu-devel] [PATCH 2/3] io: make qio_channel_yield aware of AioContexts

[Paolo Bonzini <pbonzini@redhat.com>]

Support separate coroutines for reading and writing, and
restart the coroutine on the AioContext where it was suspended on.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/io/channel.h |  7 +++---
 io/channel-socket.c  | 12 +++++-----
 io/channel.c         | 62 ++++++++++++++++++++++++++++++++++------------------
 3 files changed, 50 insertions(+), 31 deletions(-)

diff --git a/include/io/channel.h b/include/io/channel.h
index 248bc76..3030fdb 100644
--- a/include/io/channel.h
+++ b/include/io/channel.h
@@ -23,6 +23,7 @@
 
 #include "qemu-common.h"
 #include "qom/object.h"
+#include "qemu/coroutine.h"
 #include "block/aio.h"
 
 #define TYPE_QIO_CHANNEL "qio-channel"
@@ -59,8 +60,6 @@ typedef gboolean (*QIOChannelFunc)(QIOChannel *ioc,
                                    GIOCondition condition,
                                    gpointer data);
 
-typedef struct QIOChannelRestart QIOChannelRestart;
-
 /**
  * QIOChannel:
  *
@@ -84,8 +83,8 @@ struct QIOChannel {
     unsigned int features; /* bitmask of QIOChannelFeatures */
     char *name;
     AioContext *ctx;
-    QIOChannelRestart *read_coroutine;
-    QIOChannelRestart *write_coroutine;
+    Coroutine *read_coroutine;
+    Coroutine *write_coroutine;
 #ifdef _WIN32
     HANDLE event; /* For use with GSource on Win32 */
 #endif
diff --git a/io/channel-socket.c b/io/channel-socket.c
index 4d5f180..732ba20 100644
--- a/io/channel-socket.c
+++ b/io/channel-socket.c
@@ -740,14 +740,14 @@ qio_channel_socket_shutdown(QIOChannel *ioc,
     return 0;
 }
 
-static GSource *qio_channel_socket_set_fd_handler(QIOChannel *ioc,
-                                                  AioContext *ctx,
-                                                  IOHandler *io_read,
-                                                  IOHandler *io_write,
-                                                  void *opaque)
+static void qio_channel_socket_set_fd_handler(QIOChannel *ioc,
+                                              AioContext *ctx,
+                                              IOHandler *io_read,
+                                              IOHandler *io_write,
+                                              void *opaque)
 {
     QIOChannelSocket *sioc = QIO_CHANNEL_SOCKET(ioc);
-    aio_set_fd_handler(ctx, sioc->fd, false, io_read, io_write, opaque);
+    aio_set_fd_handler(ctx, sioc->fd, false, io_read, io_write, NULL, opaque);
 }
 
 static GSource *qio_channel_socket_create_watch(QIOChannel *ioc,
diff --git a/io/channel.c b/io/channel.c
index 9ef683c..d4b3a5a3 100644
--- a/io/channel.c
+++ b/io/channel.c
@@ -21,7 +21,7 @@
 #include "qemu/osdep.h"
 #include "io/channel.h"
 #include "qapi/error.h"
-#include "qemu/coroutine.h"
+#include "qemu/main-loop.h"
 
 bool qio_channel_has_feature(QIOChannel *ioc,
                              QIOChannelFeature feature)
@@ -238,22 +238,43 @@ off_t qio_channel_io_seek(QIOChannel *ioc,
 }
 
 
-typedef struct QIOChannelYieldData QIOChannelYieldData;
-struct QIOChannelYieldData {
-    QIOChannel *ioc;
-    Coroutine *co;
-};
+static void qio_channel_set_fd_handlers(QIOChannel *ioc);
+
+static void qio_channel_restart_read(void *opaque)
+{
+    QIOChannel *ioc = opaque;
+    Coroutine *co = ioc->read_coroutine;
 
+    ioc->read_coroutine = NULL;
+    qio_channel_set_fd_handlers(ioc);
+    aio_co_wake(co);
+}
 
-static gboolean qio_channel_yield_enter(QIOChannel *ioc,
-                                        GIOCondition condition,
-                                        gpointer opaque)
+static void qio_channel_restart_write(void *opaque)
 {
-    QIOChannelYieldData *data = opaque;
-    qemu_coroutine_enter(data->co);
-    return FALSE;
+    QIOChannel *ioc = opaque;
+    Coroutine *co = ioc->write_coroutine;
+
+    ioc->write_coroutine = NULL;
+    qio_channel_set_fd_handlers(ioc);
+    aio_co_wake(co);
 }
 
+static void qio_channel_set_fd_handlers(QIOChannel *ioc)
+{
+    IOHandler *rd_handler = NULL, *wr_handler = NULL;
+
+    if (ioc->read_coroutine) {
+	rd_handler = qio_channel_restart_read;
+    }
+    if (ioc->write_coroutine) {
+	rd_handler = qio_channel_restart_write;
+    }
+
+    qio_channel_set_fd_handler(ioc,
+                               ioc->ctx ? ioc->ctx : iohandler_get_aio_context(),
+                               rd_handler, wr_handler, ioc);
+}
 
 void qio_channel_set_aio_context(QIOChannel *ioc,
                                  AioContext *ctx)
@@ -272,16 +293,15 @@ void qio_channel_set_aio_context(QIOChannel *ioc,
 void coroutine_fn qio_channel_yield(QIOChannel *ioc,
                                     GIOCondition condition)
 {
-    QIOChannelYieldData data;
-
     assert(qemu_in_coroutine());
-    data.ioc = ioc;
-    data.co = qemu_coroutine_self();
-    qio_channel_add_watch(ioc,
-                          condition,
-                          qio_channel_yield_enter,
-                          &data,
-                          NULL);
+    if (condition == G_IO_IN) {
+        ioc->read_coroutine = qemu_coroutine_self();
+    } else if (condition == G_IO_OUT) {
+        ioc->write_coroutine = qemu_coroutine_self();
+    } else {
+        abort();
+    }
+    qio_channel_set_fd_handlers(ioc);
     qemu_coroutine_yield();
 }
 
-- 
2.9.3