fix possible crash at application shutdown when a race condition causes linda objects to be collected after the keeper states are cleaned up.

5 files changed, 24 insertions, 21 deletions

diff --git a/CHANGES b/CHANGES
index f6f5268..b2882e7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,8 @@
 CHANGES:
 
+CHANGE 43: BGe 09-Aug-2012
+   * fix possible crash at application shutdown when a race condition causes linda objects to be collected after the keeper states are cleaned up.
+
 CHANGE 42: BGe 06-Aug-2012
    * lanes.linda() accepts an optional name for debug purposes
 
diff --git a/src/keeper.c b/src/keeper.c
index 2404520..28dc338 100644
--- a/src/keeper.c
+++ b/src/keeper.c
@@ -63,6 +63,21 @@
 static struct s_Keeper *GKeepers = NULL;
 static int GNbKeepers = 0;
 
+static void atexit_close_keepers(void)
+{
+        int i;
+        for( i = 0; i < GNbKeepers; ++ i)
+        {
+                lua_close( GKeepers[i].L);
+                GKeepers[i].L = 0;
+                //assert( GKeepers[i].count == 0);
+                MUTEX_FREE( &GKeepers[i].lock_);
+        }
+        if( GKeepers) free( GKeepers);
+        GKeepers = NULL;
+        GNbKeepers = 0;
+}
+
 /*
 * Initialize keeper states
 *
@@ -118,6 +133,9 @@ char const* init_keepers( int const _nbKeepers, lua_CFunction _on_state_create)
                 GKeepers[i].L = K;
                 //GKeepers[i].count = 0;
         }
+        // call close_keepers at the very last as we want to be sure no thread is GCing after.
+        // (and therefore may perform linda object dereferencing after keepers are gone)
+        atexit( atexit_close_keepers);
         return NULL;    // ok
 }
 
@@ -264,18 +282,3 @@ int keeper_call( lua_State *K, char const *func_name, lua_State *L, void *linda,
         lua_settop( K, Ktos);
         return retvals;
 }
-
-void close_keepers(void)
-{
-        int i;
-        for( i = 0; i < GNbKeepers; ++ i)
-        {
-                lua_close( GKeepers[i].L);
-                GKeepers[i].L = 0;
-                //assert( GKeepers[i].count == 0);
-                MUTEX_FREE( &GKeepers[i].lock_);
-        }
-        if( GKeepers) free( GKeepers);
-        GKeepers = NULL;
-        GNbKeepers = 0;
-}
diff --git a/src/keeper.h b/src/keeper.h
index 0990846..6c4c6f9 100644
--- a/src/keeper.h
+++ b/src/keeper.h
@@ -14,7 +14,6 @@ struct s_Keeper *keeper_acquire( const void *ptr);
 void keeper_release( struct s_Keeper *K);
 void keeper_toggle_nil_sentinels( lua_State *L, int _val_i, int _nil_to_sentinel);
 int keeper_call( lua_State *K, char const *func_name, lua_State *L, void *linda, uint_t starting_index);
-void close_keepers(void);
 
 
 #endif // __keeper_h__
\ No newline at end of file
diff --git a/src/lanes.c b/src/lanes.c
index b65c6fa..262a497 100644
--- a/src/lanes.c
+++ b/src/lanes.c
@@ -1070,7 +1070,7 @@ volatile DEEP_PRELUDE *timer_deep;  // = NULL
 /*
 * Process end; cancel any still free-running threads
 */
-static int selfdestruct_atexit( lua_State *L)
+static int selfdestruct_gc( lua_State *L)
 {
     (void)L; // unused
     if (selfdestruct_first == SELFDESTRUCT_END) return 0;    // no free-running threads
@@ -1214,7 +1214,6 @@ static int selfdestruct_atexit( lua_State *L)
         DEBUGEXEC(fprintf( stderr, "Killed %d lane(s) at process end.\n", n ));
 #endif
     }
-    close_keepers();
     return 0;
 }
 
@@ -2363,7 +2362,6 @@ static void init_once_LOCKED( lua_State* L, volatile DEEP_PRELUDE** timer_deep_r
         // Selfdestruct chain handling
         //
         MUTEX_INIT( &selfdestruct_cs );
-        //atexit( selfdestruct_atexit );
 
         //---
         // Linux needs SCHED_RR to change thread priorities, and that is only
@@ -2421,7 +2419,7 @@ static void init_once_LOCKED( lua_State* L, volatile DEEP_PRELUDE** timer_deep_r
         {
             lua_newuserdata( L, 1);
             lua_newtable( L);
-            lua_pushcfunction( L, selfdestruct_atexit);
+            lua_pushcfunction( L, selfdestruct_gc);
             lua_setfield( L, -2, "__gc");
             lua_pushliteral( L, "AtExit");
             lua_setfield( L, -2, "__metatable");
diff --git a/src/lanes.lua b/src/lanes.lua
index 8cd3737..e6400df 100644
--- a/src/lanes.lua
+++ b/src/lanes.lua
@@ -255,7 +255,7 @@ end
 -- We let the C code attach methods to userdata directly
 
 -----
--- lanes.linda() -> linda_ud
+-- lanes.linda(["name"]) -> linda_ud
 --
 -- PUBLIC LANES API
 local linda = mm.linda