[gbinder] Corner cases for abandoned loopers. JB#42956

If the last GBinderIpc reference was dropped by the looper thread,
the exit flag wasn't set by gbinder_ipc_looper_stop() and such
looper thread kept hanging forever. Also, that flag wasn't checked
by gbinder_driver_read(), and even though it's even less likely
to cause any trouble in real life, let's fix that too.

src/gbinder_driver.c

@@ -953,7 +953,7 @@ gbinder_driver_read(
     if (ret >= 0) {
         /* Loop until we have handled all the incoming commands */
         gbinder_driver_handle_commands(self, reg, handler, &rb);
-        while (rb.buf.consumed) {
+        while (rb.buf.consumed && gbinder_handler_can_loop(handler)) {
             ret = gbinder_driver_write_read(self, NULL, &rb.buf);
             if (ret >= 0) {
                 gbinder_driver_handle_commands(self, reg, handler, &rb);

src/gbinder_handler.h

@@ -36,6 +36,7 @@
 #include "gbinder_types_p.h"
 
 typedef struct gbinder_handler_functions {
+    gboolean (*can_loop)(GBinderHandler* handler);
     GBinderLocalReply* (*transact)(GBinderHandler* handler,
         GBinderLocalObject* obj, GBinderRemoteRequest* req, guint code,
         guint flags, int* status);
@@ -47,6 +48,14 @@ struct gbinder_handler {
 
 /* Inline wrappers */
 
+GBINDER_INLINE_FUNC
+gboolean
+gbinder_handler_can_loop(
+    GBinderHandler* self)
+{
+    return self && self->f->can_loop && self->f->can_loop(self);
+}
+
 GBINDER_INLINE_FUNC
 GBinderLocalReply*
 gbinder_handler_transact(

src/gbinder_ipc.c

@@ -606,6 +606,16 @@ gbinder_ipc_looper_count_primary(
     return n;
 }
 
+static
+gboolean
+gbinder_ipc_looper_can_loop(
+    GBinderHandler* handler)
+{
+    GBinderIpcLooper* looper = G_CAST(handler,GBinderIpcLooper,handler);
+
+    return !g_atomic_int_get(&looper->exit);
+}
+
 static
 GBinderLocalReply*
 gbinder_ipc_looper_transact(
@@ -824,6 +834,7 @@ gbinder_ipc_looper_new(
     /* Note: this call can actually fail */
     if (!pipe(fd)) {
         static const GBinderHandlerFunctions handler_functions = {
+            .can_loop = gbinder_ipc_looper_can_loop,
             .transact = gbinder_ipc_looper_transact
         };
         GError* error = NULL;
@@ -896,13 +907,15 @@ gbinder_ipc_looper_stop(
     GBinderIpcLooper* looper)
 {
     /* Caller checks looper for NULL */
-    if (looper->thread && looper->thread != g_thread_self()) {
-        guint8 done = TX_DONE;
-
+    if (looper->thread) {
         GDEBUG("Stopping looper %s", looper->name);
         g_atomic_int_set(&looper->exit, TRUE);
-        if (write(looper->pipefd[1], &done, sizeof(done)) <= 0) {
-            looper->thread = NULL;
+        if (looper->thread != g_thread_self()) {
+            guint8 done = TX_DONE;
+
+            if (write(looper->pipefd[1], &done, sizeof(done)) <= 0) {
+                looper->thread = NULL;
+            }
         }
     }
 }
@@ -1421,7 +1434,8 @@ gbinder_ipc_tx_internal_exec(
     GBinderIpcTxPriv* priv)
 {
     static const GBinderHandlerFunctions handler_fn = {
-        gbinder_ipc_tx_handler_transact
+        .can_loop = NULL,
+        .transact = gbinder_ipc_tx_handler_transact
     };
     GBinderIpcTxInternal* tx = gbinder_ipc_tx_internal_cast(priv);
     GBinderIpcTx* pub = &priv->pub;