Handle thread crash/abort even when main thread is blocking (busy-wai…

…ting). NFC

Previously if a thread crashed when the main thread was blocked on
something (such as pthread_join) it would never get the `onerror`
message because it would never return the event loop.

emcc.py

@@ -2052,6 +2052,7 @@ def default_setting(name, new_default):
     worker_imports = [
       '__emscripten_thread_init',
       '__emscripten_thread_exit',
+      '__emscripten_thread_crashed',
       '_emscripten_tls_init',
       '_emscripten_current_thread_process_queued_calls',
       '_pthread_self',

src/worker.js

@@ -292,6 +292,9 @@ self.onmessage = (e) => {
   } catch(ex) {
     err('worker.js onmessage() captured an uncaught exception: ' + ex);
     if (ex && ex.stack) err(ex.stack);
+    if (Module['__emscripten_thread_crashed']) {
+      Module['__emscripten_thread_crashed']();
+    }
     throw ex;
   }
 };

system/lib/pthread/emscripten_futex_wait.c

@@ -8,6 +8,9 @@
 #include <errno.h>
 #include <math.h>
 #include <emscripten/threading.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
 #include "atomic.h"
 #include "threading_internal.h"
 
@@ -106,11 +109,28 @@ static int futex_wait_busy(volatile void *addr, uint32_t val, double timeout) {
   return 0;
 }
 
+static _Atomic bool thread_crashed = false;
+
+void _emscripten_thread_crashed() {
+  thread_crashed = true;
+}
+
 int emscripten_futex_wait(volatile void *addr, uint32_t val, double max_wait_ms) {
   if ((((intptr_t)addr)&3) != 0) {
     return -EINVAL;
   }
 
+  // When a secondary thread crashes, we need to be able to interrupt the main
+  // thread even if it's in a blocking/looping on a mutex.  We want to avoid
+  // using the normal proxying mechanism to send this message since it can
+  // allocate (or otherwise itself crash) so use a low level atomic primitive
+  // for this signal.
+  if (emscripten_is_main_runtime_thread() && thread_crashed) {
+    // Return the event loop so we can handle the message from the crashed
+    // thread.
+    emscripten_unwind_to_js_event_loop();
+  }
+
   int ret;
   emscripten_conditional_set_current_thread_status(EM_THREAD_STATUS_RUNNING, EM_THREAD_STATUS_WAITFUTEX);
 

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.exports

@@ -7,7 +7,8 @@ F
 G
 H
 I
-o
+J
+K
 p
 q
 r

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.funcs

@@ -16,6 +16,7 @@ $__wasm_call_ctors
 $__wasm_init_memory
 $_do_call
 $_emscripten_do_dispatch_to_thread
+$_emscripten_thread_crashed
 $_emscripten_thread_exit
 $_emscripten_thread_free_data
 $_emscripten_thread_init

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.imports

@@ -12,3 +12,4 @@ a.k
 a.l
 a.m
 a.n
+a.o

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.jssize

@@ -1 +1 @@
-47185
+47544

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.sent

@@ -12,3 +12,4 @@ k
 l
 m
 n
+o

tests/other/metadce/minimal_main_Oz_USE_PTHREADS_PROXY_TO_PTHREAD.size

@@ -1 +1 @@
-17498
+17545

tests/pthread/test_pthread_abort_interrupt.c

@@ -0,0 +1,31 @@
+// Copyright 2022 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <pthread.h>
+
+// Test that when a thread aborts the whole application crashes
+// even when the main thread is blocking in pthread_join and
+// not returning the event loop.
+
+void* thread_start(void* arg) {
+  puts("thread_start");
+  abort();
+  // Should never get here
+  __builtin_trap();
+  return NULL;
+}
+
+int main() {
+  puts("in main");
+  pthread_t t;
+  pthread_create(&t, NULL, thread_start, NULL);
+  puts("calling join");
+  pthread_join(t, NULL);
+  // Should never get here
+  __builtin_trap();
+}
+

tests/pthread/test_pthread_abort_interrupt.out

@@ -0,0 +1 @@
+Aborted(native code called abort())

tests/test_core.py

@@ -2560,6 +2560,12 @@ def test_pthread_abort(self):
     self.add_pre_run("Module.onAbort = function() { console.log('onAbort called'); }")
     self.do_run_in_out_file_test('pthread/test_pthread_abort.c', assert_returncode=NON_ZERO)
 
+  @node_pthreads
+  def test_pthread_abort_interrupt(self):
+    self.set_setting('EXIT_RUNTIME')
+    self.set_setting('PTHREAD_POOL_SIZE', 1)
+    self.do_run_in_out_file_test('pthread/test_pthread_abort_interrupt.c', assert_returncode=NON_ZERO)
+
   @no_asan('ASan does not support custom memory allocators')
   @no_lsan('LSan does not support custom memory allocators')
   @node_pthreads