macOS: workaround a keymgr/libunwind deadlock issue on x86_64 since 10.9

src/signals-mach.c

@@ -17,6 +17,18 @@
 
 #include "julia_assert.h"
 
+// private keymgr stuff
+#define KEYMGR_GCC3_DW2_OBJ_LIST 302
+enum {
+ NM_ALLOW_RECURSION = 1,
+ NM_RECURSION_ILLEGAL = 2
+};
+extern void _keymgr_set_and_unlock_processwide_ptr(unsigned int key, void *ptr);
+extern int _keymgr_unlock_processwide_ptr(unsigned int key);
+extern void *_keymgr_get_and_lock_processwide_ptr(unsigned int key);
+extern int _keymgr_get_and_lock_processwide_ptr_2(unsigned int key, void **result);
+extern int _keymgr_set_lockmode_processwide_ptr(unsigned int key, unsigned int mode);
+
 static void attach_exception_port(thread_port_t thread, int segv_only);
 
 // low 16 bits are the thread id, the next 8 bits are the original gc_state
@@ -78,6 +90,17 @@ void *mach_segv_listener(void *arg)
 
 static void allocate_segv_handler()
 {
+ // ensure KEYMGR_GCC3_DW2_OBJ_LIST is initialized, as this requires malloc
+ // and thus can deadlock when used without first initializing it.
+ // Apple caused this problem in their libunwind in 10.9 (circa keymgr-28)
+ // when they removed this part of the code from keymgr.
+ // Much thanks to Apple for providing source code, or this would probably
+ // have simply remained unsolved forever on their platform.
+ // This is similar to just calling checkKeyMgrRegisteredFDEs
+ // (this is quite thread-unsafe)
+ if (_keymgr_set_lockmode_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST, NM_ALLOW_RECURSION))
+ jl_error("_keymgr_set_lockmode_processwide_ptr failed");
+
  arraylist_new(&suspended_threads, jl_n_threads);
  pthread_t thread;
  pthread_attr_t attr;
@@ -463,6 +486,8 @@ void *mach_profile_listener(void *arg)
  // sample each thread, round-robin style in reverse order
  // (so that thread zero gets notified last)
  jl_lock_profile();
+ void *unused = NULL;
+ int keymgr_locked = _keymgr_get_and_lock_processwide_ptr_2(KEYMGR_GCC3_DW2_OBJ_LIST, &unused) == 0;
  for (i = jl_n_threads; i-- > 0; ) {
  // if there is no space left, break early
  if (bt_size_cur >= bt_size_max - 1)
@@ -511,6 +536,8 @@ void *mach_profile_listener(void *arg)
  // We're done! Resume the thread.
  jl_thread_resume(i, 0);
  }
+ if (keymgr_locked)
+ _keymgr_unlock_processwide_ptr(KEYMGR_GCC3_DW2_OBJ_LIST);
  jl_unlock_profile();
  if (running) {
  // Reset the alarm