[Qemu-devel] [PATCH v2 07/15] qio/chardev: update net listener gcontext

[Peter Xu]

TCP chardevs can be using QIO network listeners working in the
background when in listening mode.  However the network listeners are
always running in main context.  This can race with chardevs that are
running in non-main contexts.

To solve this, we need to re-setup the net listeners in
tcp_chr_update_read_handler() with the newly cached gcontext.

Since at it, generalize a tcp_chr_net_listener_setup() helper function
and clean up the old code a bit.

Signed-off-by: Peter Xu <address@hidden>
---
 chardev/char-socket.c | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/chardev/char-socket.c b/chardev/char-socket.c
index 43a2cc2c1c..5cd20cc932 100644
--- a/chardev/char-socket.c
+++ b/chardev/char-socket.c
@@ -410,6 +410,19 @@ static void update_disconnected_filename(SocketChardev *s)
                                          s->is_listen, s->is_telnet);
 }
 
+/* Set enable=true to start net listeners, false to stop them. */
+static void tcp_chr_net_listener_setup(SocketChardev *s, bool enable)
+{
+    Chardev *chr = CHARDEV(s);
+
+    /* Net listeners' context will follow the Chardev's. */
+    qio_net_listener_set_client_func_full(s->listener,
+                                          enable ? tcp_chr_accept : NULL,
+                                          enable ? chr : NULL,
+                                          NULL,
+                                          chr->gcontext);
+}
+
 /* NB may be called even if tcp_chr_connect has not been
  * reached, due to TLS or telnet initialization failure,
  * so can *not* assume s->connected == true
@@ -422,8 +435,7 @@ static void tcp_chr_disconnect(Chardev *chr)
     tcp_chr_free_connection(chr);
 
     if (s->listener) {
-        qio_net_listener_set_client_func(s->listener, tcp_chr_accept,
-                                         chr, NULL);
+        tcp_chr_net_listener_setup(s, true);
     }
     update_disconnected_filename(s);
     if (emit_close) {
@@ -559,6 +571,15 @@ static void tcp_chr_update_read_handler(Chardev *chr)
 {
     SocketChardev *s = SOCKET_CHARDEV(chr);
 
+    if (s->listener) {
+        /*
+         * It's possible that chardev context is changed in
+         * qemu_chr_be_update_read_handlers().  Reset it for QIO net
+         * listener if there is.
+         */
+        tcp_chr_net_listener_setup(s, true);
+    }
+
     if (!s->connected) {
         return;
     }
@@ -742,7 +763,7 @@ static int tcp_chr_new_client(Chardev *chr, 
QIOChannelSocket *sioc)
         qio_channel_set_delay(s->ioc, false);
     }
     if (s->listener) {
-        qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL);
+        tcp_chr_net_listener_setup(s, false);
     }
 
     if (s->tls_creds) {
@@ -823,7 +844,7 @@ static void char_socket_finalize(Object *obj)
     tcp_chr_reconn_timer_cancel(s);
     qapi_free_SocketAddress(s->addr);
     if (s->listener) {
-        qio_net_listener_set_client_func(s->listener, NULL, NULL, NULL);
+        tcp_chr_net_listener_setup(s, false);
         object_unref(OBJECT(s->listener));
     }
     if (s->tls_creds) {
@@ -979,8 +1000,7 @@ static void qmp_chardev_open_socket(Chardev *chr,
                 return;
             }
             if (!s->ioc) {
-                qio_net_listener_set_client_func(s->listener, tcp_chr_accept,
-                                                 chr, NULL);
+                tcp_chr_net_listener_setup(s, true);
             }
         } else if (qemu_chr_wait_connected(chr, errp) < 0) {
             goto error;
-- 
2.14.3