fix keeper state stack accumulating garbage in case of transfer errors

5 files changed, 12 insertions, 2 deletions

diff --git a/CHANGES b/CHANGES
index 34bd2d9..91849d7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,8 @@
 CHANGES:
 
+CHANGE 161: BGe 15-Apr-24
+   * fix keeper state stack accumulating garbage in case of transfer errors
+
 CHANGE 160: BGe 11-Apr-24
    * add manual control over GC behavior in keeper states
    * update a bunch of test scripts
diff --git a/Makefile b/Makefile
index 08888e4..9939f73 100644
--- a/Makefile
+++ b/Makefile
@@ -77,6 +77,7 @@ test:
         $(MAKE) basic
         $(MAKE) cancel
         $(MAKE) cyclic
+        $(MAKE) deadlock
         $(MAKE) errhangtest
         $(MAKE) fibonacci
         $(MAKE) fifo
diff --git a/src/keeper.c b/src/keeper.c
index a1505b7..1522718 100644
--- a/src/keeper.c
+++ b/src/keeper.c
@@ -810,7 +810,9 @@ int keeper_call( Universe* U, lua_State* K, keeper_api_t func_, lua_State* L, vo
     int const Ktos = lua_gettop( K);
     int retvals = -1;
 
-    STACK_GROW( K, 2);
+    // if we didn't do anything wrong, the keeper stack should be clean
+    ASSERT_L(Ktos == 0);
+    STACK_GROW(K, 2);
 
     PUSH_KEEPER_FUNC( K, func_);
 
diff --git a/src/linda.c b/src/linda.c
index 2128520..d92f5f2 100644
--- a/src/linda.c
+++ b/src/linda.c
@@ -90,12 +90,16 @@ LUAG_FUNC( linda_protected_call)
     Keeper* K = keeper_acquire( linda->U->keepers, LINDA_KEEPER_HASHSEED(linda));
     lua_State* KL = K ? K->L : NULL; // need to do this for 'STACK_CHECK'
     if( KL == NULL) return 0;
+    // if we didn't do anything wrong, the keeper stack should be clean
+    ASSERT_L(lua_gettop(KL) == 0);
 
     // retrieve the actual function to be called and move it before the arguments
     lua_pushvalue( L, lua_upvalueindex( 1));
     lua_insert( L, 1);
     // do a protected call
     rc = lua_pcall( L, lua_gettop( L) - 1, LUA_MULTRET, 0);
+    // whatever happens, the keeper state stack must be empty when we are done
+    lua_settop(KL, 0);
 
     // release the keeper
     keeper_release( K);
diff --git a/tests/deadlock.lua b/tests/deadlock.lua
index 73d7ccb..c85d99f 100644
--- a/tests/deadlock.lua
+++ b/tests/deadlock.lua
@@ -1,7 +1,7 @@
 -- this script tests the fix of a bug that could cause the mutex of a keeper state to remain locked
 -- see https://github.com/LuaLanes/lanes/commit/0cc1c9c9dcea5955f7dab921d9a2fff78c4e1729
 
-local lanes = require('lanes').configure()
+local lanes = require('lanes').configure{with_timers=false}
 local linda = lanes.linda "deadlock_linda"
 
 print "let's begin"