[0.8 branch] server: add main_dispatcher

add main_dispatcher, a message passing mechanism for sending messages to
the main thread. The main thread is the thread that implements
SpiceCoreInterface, which is assumed to be a single thread.

Similar to the async operation of red_worker, a socket pair is created
and used to pass messages. The messages are a fixed size to ease
parsing. A single message is defined to pass a channel_event.

RHBZ: 746950
FDBZ: 41858

This patch is 0.8 branch only, for the master branch there should be a
better approach to share code with red_dispatcher and ready the way for
later adding more threads.

cherry-pick from 0.8 80caf07e09

Conflicts:

	server/reds.c

server/Makefile.am

@@ -80,6 +80,8 @@ libspice_server_la_SOURCES =			\
 	red_common.h				\
 	red_dispatcher.c			\
 	red_dispatcher.h			\
+	main_dispatcher.c			\
+	main_dispatcher.h			\
 	red_memslots.c				\
 	red_memslots.h				\
 	red_parse_qxl.c				\

server/main_dispatcher.c

@@ -0,0 +1,145 @@
+#include <unistd.h>
+#include <string.h>
+#include <errno.h>
+#include <pthread.h>
+#include <assert.h>
+
+#include "red_common.h"
+#include "main_dispatcher.h"
+
+/*
+ * Main Dispatcher
+ * ===============
+ *
+ * Communication channel between any non main thread and the main thread.
+ *
+ * The main thread is that from which spice_server_init is called.
+ *
+ * Messages are single sized, sent from the non-main thread to the main-thread.
+ * No acknowledge is sent back. This prevents a possible deadlock with the main
+ * thread already waiting on a response for the existing red_dispatcher used
+ * by the worker thread.
+ *
+ * All events have three functions:
+ * main_dispatcher_<event_name> - non static, public function
+ * main_dispatcher_self_<event_name> - handler for main thread
+ * main_dispatcher_handle_<event_name> - handler for callback from main thread
+ *   seperate from self because it may send an ack or do other work in the future.
+ */
+
+typedef struct {
+    SpiceCoreInterface *core;
+    int main_fd;
+    int other_fd;
+    pthread_t self;
+    pthread_mutex_t lock;
+} MainDispatcher;
+
+MainDispatcher main_dispatcher;
+
+enum {
+    MAIN_DISPATCHER_CHANNEL_EVENT = 0,
+
+    MAIN_DISPATCHER_NUM_MESSAGES
+};
+
+typedef struct MainDispatcherMessage {
+    uint32_t type;
+    union {
+        struct {
+            int event;
+            SpiceChannelEventInfo *info;
+        } channel_event;
+    } data;
+} MainDispatcherMessage;
+
+/* channel_event - calls core->channel_event, must be done in main thread */
+static void main_dispatcher_self_handle_channel_event(
+                                                int event,
+                                                SpiceChannelEventInfo *info)
+{
+    main_dispatcher.core->channel_event(event, info);
+}
+
+static void main_dispatcher_handle_channel_event(MainDispatcherMessage *msg)
+{
+    main_dispatcher_self_handle_channel_event(msg->data.channel_event.event,
+                                              msg->data.channel_event.info);
+}
+
+void main_dispatcher_channel_event(int event, SpiceChannelEventInfo *info)
+{
+    MainDispatcherMessage msg;
+    ssize_t written = 0;
+    ssize_t ret;
+
+    if (pthread_self() == main_dispatcher.self) {
+        main_dispatcher_self_handle_channel_event(event, info);
+        return;
+    }
+    msg.type = MAIN_DISPATCHER_CHANNEL_EVENT;
+    msg.data.channel_event.event = event;
+    msg.data.channel_event.info = info;
+    pthread_mutex_lock(&main_dispatcher.lock);
+    while (written < sizeof(msg)) {
+        ret = write(main_dispatcher.other_fd, &msg + written,
+                    sizeof(msg) - written);
+        if (ret == -1) {
+            assert(errno == EINTR);
+            continue;
+        }
+        written += ret;
+    }
+    pthread_mutex_unlock(&main_dispatcher.lock);
+}
+
+
+static void main_dispatcher_handle_read(int fd, int event, void *opaque)
+{
+    int ret;
+    MainDispatcher *md = opaque;
+    MainDispatcherMessage msg;
+    int read_size = 0;
+
+    while (read_size < sizeof(msg)) {
+        /* blocks until sizeof(msg) is read */
+        ret = read(md->main_fd, &msg + read_size, sizeof(msg) - read_size);
+        if (ret == -1) {
+            if (errno != EINTR) {
+                red_printf("error reading from main dispatcher: %d\n", errno);
+                /* TODO: close channel? */
+                return;
+            }
+            continue;
+        }
+        read_size += ret;
+    }
+    switch (msg.type) {
+        case MAIN_DISPATCHER_CHANNEL_EVENT:
+            main_dispatcher_handle_channel_event(&msg);
+            break;
+        default:
+            red_printf("error: unhandled main dispatcher message type %d\n",
+                       msg.type);
+    }
+}
+
+void main_dispatcher_init(SpiceCoreInterface *core)
+{
+    int channels[2];
+
+    memset(&main_dispatcher, 0, sizeof(main_dispatcher));
+    main_dispatcher.core = core;
+
+    if (socketpair(AF_LOCAL, SOCK_STREAM, 0, channels) == -1) {
+        red_error("socketpair failed %s", strerror(errno));
+        return;
+    }
+    pthread_mutex_init(&main_dispatcher.lock, NULL);
+    main_dispatcher.main_fd = channels[0];
+    main_dispatcher.other_fd = channels[1];
+    main_dispatcher.self = pthread_self();
+
+    core->watch_add(main_dispatcher.main_fd, SPICE_WATCH_EVENT_READ,
+                    main_dispatcher_handle_read, &main_dispatcher);
+}

server/main_dispatcher.h

@@ -0,0 +1,9 @@
+#ifndef MAIN_DISPATCHER_H
+#define MAIN_DISPATCHER_H
+
+#include <spice.h>
+
+void main_dispatcher_channel_event(int event, SpiceChannelEventInfo *info);
+void main_dispatcher_init(SpiceCoreInterface *core);
+
+#endif //MAIN_DISPATCHER_H

server/reds.c

@@ -56,6 +56,7 @@
 #include "main_channel.h"
 #include "red_common.h"
 #include "red_dispatcher.h"
+#include "main_dispatcher.h"
 #include "snd_worker.h"
 #include <spice/stats.h>
 #include "stat.h"
@@ -322,7 +323,7 @@ static void reds_stream_channel_event(RedsStream *s, int event)
 {
     if (core->base.minor_version < 3 || core->channel_event == NULL)
         return;
-    core->channel_event(event, &s->info);
+    main_dispatcher_channel_event(event, &s->info);
 }
 
 static ssize_t stream_write_cb(RedsStream *s, const void *buf, size_t size)
@@ -3519,6 +3520,7 @@ static int do_spice_init(SpiceCoreInterface *core_interface)
     init_vd_agent_resources();
     ring_init(&reds->clients);
     reds->num_clients = 0;
+    main_dispatcher_init(core);
 
     if (!(reds->mig_timer = core->timer_add(migrate_timout, NULL))) {
         red_error("migration timer create failed");