[Emacs-diffs] Changes to emacs/src/alloc.c

[Jan Djärv]

Index: emacs/src/alloc.c
diff -c emacs/src/alloc.c:1.354 emacs/src/alloc.c:1.355
*** emacs/src/alloc.c:1.354     Tue Dec  7 08:25:43 2004
--- emacs/src/alloc.c   Tue Dec  7 17:38:30 2004
***************
*** 91,96 ****
--- 91,113 ----
  
  #if ! defined (SYSTEM_MALLOC) && defined (HAVE_GTK_AND_PTHREAD)
  
+ /* When GTK uses the file chooser dialog, different backends can be loaded
+    dynamically.  One such a backend is the Gnome VFS backend that gets loaded
+    if you run Gnome.  That backend creates several threads and also allocates
+    memory with malloc.
+ 
+    If Emacs sets malloc hooks (! SYSTEM_MALLOC) and the emacs_blocked_*
+    functions below are called from malloc, there is a chance that one
+    of these threads preempts the Emacs main thread and the hook variables
+    end up in a inconsistent state.  So we have a mutex to prevent that (note
+    that the backend handles concurrent access to malloc within its own threads
+    but Emacs code running in the main thread is not included in that control).
+ 
+    When UNBLOCK_INPUT is called, revoke_input_signal may be called.  If this
+    happens in one of the backend threads we will have two threads that tries
+    to run Emacs code at once, and the code is not prepared for that.
+    To prevent that, we only call BLOCK/UNBLOCK from the main thread.  */
+ 
  static pthread_mutex_t alloc_mutex;
  pthread_t main_thread;