efl: ecore thread safety (remove option, keep code, add instructions).

* remove the option, as it shouldn't really exist.

 * keep code, as requested by Cedric, someone may fix it someday. And
   the default is the DISABLED, as the enable was broken.

 * Add instructions on how to solve the problem, if a brave folk is up
   to it.



SVN revision: 80352

configure.ac

@@ -1953,20 +1953,6 @@ AC_ARG_ENABLE([g-main-loop],
    ],
    [want_g_main_loop="no"])
 
-# thread safety
-
-AC_ARG_ENABLE([thread-safety],
-   [AC_HELP_STRING([--enable-thread-safety],
-       [enable thread safety. @<:@default=disabled@:>@])],
-   [
-    if test "x${enableval}" = "xyes" ; then
-       want_thread_safety="yes"
-    else
-       want_thread_safety="no"
-    fi
-   ],
-   [want_thread_safety="no"])
-
 # epoll
 
 AC_ARG_ENABLE([epoll],
@@ -1994,10 +1980,6 @@ if test "x${with_glib}" = "xyes" || test "x${with_glib}" = "xalways" ; then
    want_glib="yes"
 fi
 
-if test "x${want_thread_safety}" = "xyes" ; then
-   AC_DEFINE([HAVE_THREAD_SAFETY], [1], [Define to enable thread safety])
-fi
-
 want_ecore_timer_dump="no"
 if test "x${build_profile}" = "xdebug" && test "x${ac_cv_func_backtrace}" = "xyes"; then
    want_ecore_timer_dump="yes"
@@ -4164,7 +4146,6 @@ echo "    Tiled 32BPP rotate......: $have_tile_rotate"
 echo
 
 echo "Ecore:"
-echo "  Thread safety..............: $want_thread_safety"
 echo "  GLib support...............: $with_glib"
 echo "  Use g_main_loop............: $want_g_main_loop"
 echo "  Gathering memory statistic.: $ac_cv_func_mallinfo"

src/lib/ecore/ecore_private.h

@@ -247,6 +247,25 @@ static inline void
 _ecore_lock(void)
 {
 #ifdef HAVE_THREAD_SAFETY
+   /* THIS IS BROKEN AND NEEDS FIXING
+    *
+    * the concept of lock to execute main-loop related functions is okay
+    * and the code below is correct per se, but with its usage in Ecore
+    * is leading to hard locks that must be investigated.
+    *
+    * One failure possibility is missing _ecore_unlock() that leaves
+    * the lock taken and on next take it will block.
+    *
+    * Another failure possibility is one function that takes the lock
+    * and calls some API function that also takes the lock, leading to
+    * block.
+    *
+    * When these are fixed, remove the HAVE_THREAD_SAFETY and leave it
+    * always on. To eliminate the lock overhead for non-threaded
+    * applications, have a global boolean that is set to TRUE by user
+    * if he uses this features, much like eina_log_threads_enable().
+    *  -- Gustavo, December 6th 2012.
+    */
    eina_lock_take(&_ecore_main_loop_lock);
 #else
    /* at least check we're not being called from a thread */