Move thread exit code to native. NFC (#14853)

Author: sbc100

emcc.py

@@ -1864,7 +1864,6 @@ def default_setting(name, new_default):
     settings.JS_LIBRARIES.append((0, 'library_pthread.js'))
     settings.EXPORTED_FUNCTIONS += [
       '___emscripten_pthread_data_constructor',
-      '___pthread_tsd_run_dtors',
       '__emscripten_call_on_thread',
       '__emscripten_main_thread_futex',
       '__emscripten_thread_init',

src/library_pthread.js

@@ -128,18 +128,6 @@ var LibraryPThread = {
     },
 #endif
 
-    runExitHandlers: function() {
-      while (PThread.threadExitHandlers.length > 0) {
-        PThread.threadExitHandlers.pop()();
-      }
-
-      // Call into the musl function that runs destructors of all thread-specific data.
-#if ASSERTIONS
-      assert(_pthread_self())
-#endif
-      ___pthread_tsd_run_dtors();
-    },
-
     setExitStatus: function(status) {
       EXITSTATUS = status;
     },
@@ -949,39 +937,26 @@ var LibraryPThread = {
     return wasDetached ? {{{ cDefine('EINVAL') }}} : 0;
   },
 
-  __pthread_exit_js__deps: ['exit'],
-  __pthread_exit_js: function(status) {
-    // Called when we are performing a pthread_exit(), either explicitly called
+  __pthread_exit_run_handlers__deps: ['exit'],
+  __pthread_exit_run_handlers: function(status) {
+    // Called from pthread_exit, either when called explicitly called
     // by programmer, or implicitly when leaving the thread main function.
-    if (!ENVIRONMENT_IS_PTHREAD) {
-      PThread.runExitHandlers();
-      _exit(status);
-      // unreachable
-
-    }
 
-    var tb = _pthread_self();
 #if PTHREADS_DEBUG
+    var tb = _pthread_self();
     assert(tb);
     out('Pthread 0x' + tb.toString(16) + ' exited.');
 #endif
 
-    // Disable all cancellation so that executing the cleanup handlers won't trigger another JS
-    // canceled exception to be thrown.
-    Atomics.store(HEAPU32, (tb + {{{ C_STRUCTS.pthread.canceldisable }}} ) >> 2, 1/*PTHREAD_CANCEL_DISABLE*/);
-    Atomics.store(HEAPU32, (tb + {{{ C_STRUCTS.pthread.cancelasync }}} ) >> 2, 0/*PTHREAD_CANCEL_DEFERRED*/);
-    PThread.runExitHandlers();
-
-    Atomics.store(HEAPU32, (tb + {{{ C_STRUCTS.pthread.result }}} ) >> 2, status);
-    // When we publish this, the main thread is free to deallocate the thread object and we are done.
-    // Therefore set _pthread_self = 0; above to 'release' the object in this worker thread.
-    Atomics.store(HEAPU32, (tb + {{{ C_STRUCTS.pthread.threadStatus }}} ) >> 2, 1); // Mark the thread as no longer running.
-
-    _emscripten_futex_wake(tb + {{{ C_STRUCTS.pthread.threadStatus }}}, {{{ cDefine('INT_MAX') }}}); // wake all threads
-
-    // Not hosting a pthread anymore in this worker, reset the info structures to null.
-    __emscripten_thread_init(0, 0, 0); // Unregister the thread block inside the wasm module.
+    while (PThread.threadExitHandlers.length > 0) {
+      PThread.threadExitHandlers.pop()();
+    }
+  },
 
+  __pthread_exit_done: function() {
+    // Called at the end of pthread_exit, either when called explicitly called
+    // by programmer, or implicitly when leaving the thread main function.
+    //
     // Note: in theory we would like to return any offscreen canvases back to the main thread,
     // but if we ever fetched a rendering context for them that would not be valid, so we don't try.
     postMessage({ 'cmd': 'exit' });

system/lib/pthread/pthread_create.c

@@ -16,9 +16,16 @@
 
 extern int __cxa_thread_atexit(void (*)(void *), void *, void *);
 extern int __pthread_create_js(pthread_t *thread, const pthread_attr_t *attr, void *(*start_routine) (void *), void *arg);
-extern void __pthread_exit_js(void* status);
+extern void _emscripten_thread_init(int, int, int);
+extern void __pthread_exit_run_handlers();
+extern void __pthread_exit_done();
 extern int8_t __dso_handle;
 
+static void dummy_0()
+{
+}
+weak_alias(dummy_0, __pthread_tsd_run_dtors);
+
 void __run_cleanup_handlers(void* _unused) {
   pthread_t self = __pthread_self();
   while (self->cancelbuf) {
@@ -48,9 +55,35 @@ int __pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*star
   return __pthread_create_js(thread, attr, start_routine, arg);
 }
 
-void _emscripten_thread_exit(void* retval) {
-  assert(pthread_self());
-  __pthread_exit_js(retval);
+void _emscripten_thread_exit(void* result) {
+  struct pthread *self = __pthread_self();
+  assert(self);
+
+  self->canceldisable = PTHREAD_CANCEL_DISABLE;
+  self->cancelasync = PTHREAD_CANCEL_DEFERRED;
+  self->result = result;
+
+  __pthread_exit_run_handlers();
+
+  // Call into the musl function that runs destructors of all thread-specific data.
+  __pthread_tsd_run_dtors();
+
+  if (self == emscripten_main_browser_thread_id()) {
+    // FIXME(sbc): When pthread_exit causes the entire application to exit
+    // we should be returning zero (according to the man page for pthread_exit).
+    exit((intptr_t)result);
+    return;
+  }
+
+  // Mark the thread as no longer running.
+  // When we publish this, the main thread is free to deallocate the thread object and we are done.
+  self->threadStatus = 1;
+
+  emscripten_futex_wake(&self->threadStatus, INT_MAX); // wake all threads
+
+  // Not hosting a pthread anymore in this worker, reset the info structures to null.
+  _emscripten_thread_init(0, 0, 0); // Unregister the thread block inside the wasm module.
+  __pthread_exit_done();
 }
 
 // Mark as `no_sanitize("address"` since emscripten_pthread_exit destroys

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.exports

@@ -14,8 +14,7 @@ M
 N
 O
 P
-t
-u
+Q
 v
 w
 x

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.funcs

@@ -7,7 +7,6 @@ $__pthread_mutex_trylock
 $__pthread_mutex_unlock
 $__pthread_self_internal
 $__pthread_setcancelstate
-$__pthread_tsd_run_dtors
 $__wasm_call_ctors
 $__wasm_init_memory
 $_do_call

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.imports

@@ -17,3 +17,5 @@ a.p
 a.q
 a.r
 a.s
+a.t
+a.u

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.sent

@@ -17,3 +17,5 @@ p
 q
 r
 s
+t
+u