Kill the server only after some delay

Let the server terminate properly once all the sockets are closed.

If it does not terminate (this can happen if the device is asleep), then
kill it.

Fixes #1992 <https://github.com/Genymobile/scrcpy/issues/1992>

app/src/server.c

@@ -11,6 +11,7 @@
 
 #include "config.h"
 #include "command.h"
+#include "util/lock.h"
 #include "util/log.h"
 #include "util/net.h"
 #include "util/str_util.h"
@@ -361,6 +362,19 @@ server_init(struct server *server) {
     atomic_flag_clear_explicit(&server->server_socket_closed,
                                memory_order_relaxed);
 
+    server->mutex = SDL_CreateMutex();
+    if (!server->mutex) {
+        return false;
+    }
+
+    server->process_terminated_cond = SDL_CreateCond();
+    if (!server->process_terminated_cond) {
+        SDL_DestroyMutex(server->mutex);
+        return false;
+    }
+
+    server->process_terminated = false;
+
     server->server_socket = INVALID_SOCKET;
     server->video_socket = INVALID_SOCKET;
     server->control_socket = INVALID_SOCKET;
@@ -387,6 +401,12 @@ run_wait_server(void *data) {
         // unblocked by closesocket(). Therefore, call both (close_socket()).
         close_socket(server->server_socket);
     }
+
+    mutex_lock(server->mutex);
+    server->process_terminated = true;
+    cond_signal(server->process_terminated_cond);
+    mutex_unlock(server->mutex);
+
     LOGD("Server terminated");
     return 0;
 }
@@ -510,17 +530,36 @@ server_stop(struct server *server) {
 
     assert(server->process != PROCESS_NONE);
 
-    cmd_terminate(server->process);
-
     if (server->tunnel_enabled) {
         // ignore failure
         disable_tunnel(server);
     }
 
+    // Give some delay for the server to terminate properly
+    mutex_lock(server->mutex);
+    int r = 0;
+    if (!server->process_terminated) {
+#define WATCHDOG_DELAY_MS 2000
+        r = cond_wait_timeout(server->process_terminated_cond,
+                              server->mutex,
+                              WATCHDOG_DELAY_MS);
+    }
+    mutex_unlock(server->mutex);
+
+    // After this delay, kill the server.
+    // On some devices, closing the sockets is not sufficient to wake up the
+    // blocking calls while the device is asleep.
+    if (r == SDL_MUTEX_TIMEDOUT) {
+        LOGW("Killing the server");
+        cmd_terminate(server->process);
+    }
+
     SDL_WaitThread(server->wait_server_thread, NULL);
 }
 
 void
 server_destroy(struct server *server) {
     SDL_free(server->serial);
+    SDL_DestroyCond(server->process_terminated_cond);
+    SDL_DestroyMutex(server->mutex);
 }

app/src/server.h

@@ -18,6 +18,11 @@ struct server {
     process_t process;
     SDL_Thread *wait_server_thread;
     atomic_flag server_socket_closed;
+
+    SDL_mutex *mutex;
+    SDL_cond *process_terminated_cond;
+    bool process_terminated;
+
     socket_t server_socket; // only used if !tunnel_forward
     socket_t video_socket;
     socket_t control_socket;