iohandler: Use aio API

iohandler.c shares the same interface with aio, but with duplicated
code. It's better to rebase iohandler, also because that aio is a
more friendly interface to multi-threads.

Create a global AioContext instance and let its GSource handle the
iohandler events.

Signed-off-by: Fam Zheng <famz@redhat.com>
Message-Id: <1441596538-4412-1-git-send-email-famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

include/qemu/main-loop.h

@@ -203,6 +203,7 @@ void qemu_set_fd_handler(int fd,
                          IOHandler *fd_write,
                          void *opaque);
 
+GSource *iohandler_get_g_source(void);
 #ifdef CONFIG_POSIX
 /**
  * qemu_add_child_watch: Register a child process for reaping.
@@ -265,8 +266,6 @@ void qemu_mutex_unlock_iothread(void);
 /* internal interfaces */
 
 void qemu_fd_register(int fd);
-void qemu_iohandler_fill(GArray *pollfds);
-void qemu_iohandler_poll(GArray *pollfds, int rc);
 
 QEMUBH *qemu_bh_new(QEMUBHFunc *cb, void *opaque);
 void qemu_bh_schedule_idle(QEMUBH *bh);

iohandler.c

@@ -32,111 +32,30 @@
 #include <sys/wait.h>
 #endif
 
-typedef struct IOHandlerRecord {
-    IOHandler *fd_read;
-    IOHandler *fd_write;
-    void *opaque;
-    QLIST_ENTRY(IOHandlerRecord) next;
-    int fd;
-    int pollfds_idx;
-    bool deleted;
-} IOHandlerRecord;
-
-static QLIST_HEAD(, IOHandlerRecord) io_handlers =
-    QLIST_HEAD_INITIALIZER(io_handlers);
+/* This context runs on top of main loop. We can't reuse qemu_aio_context
+ * because iohandlers mustn't be polled by aio_poll(qemu_aio_context). */
+static AioContext *iohandler_ctx;
 
-void qemu_set_fd_handler(int fd,
-                         IOHandler *fd_read,
-                         IOHandler *fd_write,
-                         void *opaque)
+static void iohandler_init(void)
 {
-    IOHandlerRecord *ioh;
-
-    assert(fd >= 0);
-
-    if (!fd_read && !fd_write) {
-        QLIST_FOREACH(ioh, &io_handlers, next) {
-            if (ioh->fd == fd) {
-                ioh->deleted = 1;
-                break;
-            }
-        }
-    } else {
-        QLIST_FOREACH(ioh, &io_handlers, next) {
-            if (ioh->fd == fd)
-                goto found;
-        }
-        ioh = g_malloc0(sizeof(IOHandlerRecord));
-        QLIST_INSERT_HEAD(&io_handlers, ioh, next);
-    found:
-        ioh->fd = fd;
-        ioh->fd_read = fd_read;
-        ioh->fd_write = fd_write;
-        ioh->opaque = opaque;
-        ioh->pollfds_idx = -1;
-        ioh->deleted = 0;
-        qemu_notify_event();
+    if (!iohandler_ctx) {
+        iohandler_ctx = aio_context_new(&error_abort);
     }
 }
 
-void qemu_iohandler_fill(GArray *pollfds)
+GSource *iohandler_get_g_source(void)
 {
-    IOHandlerRecord *ioh;
-
-    QLIST_FOREACH(ioh, &io_handlers, next) {
-        int events = 0;
-
-        if (ioh->deleted)
-            continue;
-        if (ioh->fd_read) {
-            events |= G_IO_IN | G_IO_HUP | G_IO_ERR;
-        }
-        if (ioh->fd_write) {
-            events |= G_IO_OUT | G_IO_ERR;
-        }
-        if (events) {
-            GPollFD pfd = {
-                .fd = ioh->fd,
-                .events = events,
-            };
-            ioh->pollfds_idx = pollfds->len;
-            g_array_append_val(pollfds, pfd);
-        } else {
-            ioh->pollfds_idx = -1;
-        }
-    }
+    iohandler_init();
+    return aio_get_g_source(iohandler_ctx);
 }
 
-void qemu_iohandler_poll(GArray *pollfds, int ret)
+void qemu_set_fd_handler(int fd,
+                         IOHandler *fd_read,
+                         IOHandler *fd_write,
+                         void *opaque)
 {
-    if (ret > 0) {
-        IOHandlerRecord *pioh, *ioh;
-
-        QLIST_FOREACH_SAFE(ioh, &io_handlers, next, pioh) {
-            int revents = 0;
-
-            if (!ioh->deleted && ioh->pollfds_idx != -1) {
-                GPollFD *pfd = &g_array_index(pollfds, GPollFD,
-                                              ioh->pollfds_idx);
-                revents = pfd->revents;
-            }
-
-            if (!ioh->deleted && ioh->fd_read &&
-                (revents & (G_IO_IN | G_IO_HUP | G_IO_ERR))) {
-                ioh->fd_read(ioh->opaque);
-            }
-            if (!ioh->deleted && ioh->fd_write &&
-                (revents & (G_IO_OUT | G_IO_ERR))) {
-                ioh->fd_write(ioh->opaque);
-            }
-
-            /* Do this last in case read/write handlers marked it for deletion */
-            if (ioh->deleted) {
-                QLIST_REMOVE(ioh, next);
-                g_free(ioh);
-            }
-        }
-    }
+    iohandler_init();
+    aio_set_fd_handler(iohandler_ctx, fd, fd_read, fd_write, opaque);
 }
 
 /* reaping of zombies.  right now we're not passing the status to

main-loop.c

@@ -161,6 +161,9 @@ int qemu_init_main_loop(Error **errp)
     src = aio_get_g_source(qemu_aio_context);
     g_source_attach(src, NULL);
     g_source_unref(src);
+    src = iohandler_get_g_source();
+    g_source_attach(src, NULL);
+    g_source_unref(src);
     return 0;
 }
 
@@ -487,7 +490,6 @@ int main_loop_wait(int nonblocking)
 #ifdef CONFIG_SLIRP
     slirp_pollfds_fill(gpollfds, &timeout);
 #endif
-    qemu_iohandler_fill(gpollfds);
 
     if (timeout == UINT32_MAX) {
         timeout_ns = -1;
@@ -500,7 +502,6 @@ int main_loop_wait(int nonblocking)
                                           &main_loop_tlg));
 
     ret = os_host_main_loop_wait(timeout_ns);
-    qemu_iohandler_poll(gpollfds, ret);
 #ifdef CONFIG_SLIRP
     slirp_pollfds_poll(gpollfds, (ret < 0));
 #endif