TASK-194243 debug double unlock

Author: balupillai

src/ldo.c

@@ -69,6 +69,9 @@ void luaD_throw (lua_State *L, int errcode) {
     LUAI_THROW(L, L->errorJmp);
   }
   else {
+    thrlua_log(L, DCRITICAL,
+      "luaD_throw: no error handler, errcode=%d, L=%p, invoking panic",
+      errcode, (void *)L);
     L->status = cast_byte(errcode);
     if (G(L)->panic) {
       resetstack(L, errcode);

src/thrlua.h

@@ -254,6 +254,22 @@ extern void lua_do_longjmp(luai_jmpbuf env, int val)
 #define LUAI_TRY_END(L) \
   (L)->errorJmp = lj.previous; \
   if (lj.status) { \
+    /* Log the error and re-throw path for diagnostics. */ \
+    thrlua_log((L), DCRITICAL, \
+      "LUAI_TRY_END: error status=%d in TRY block at %s:%d, " \
+      "re-throwing with %s outer handler, L=%p", \
+      lj.status, lj.file, lj.line, \
+      lj.previous ? "an" : "NO", (void *)(L)); \
+    /* Re-acquire the lock before re-throwing.  The LUAI_TRY_FINALLY \
+     * block has already called lua_unlock(), but luaD_throw() expects \
+     * the lock to be held: if there is an outer error handler its \
+     * FINALLY will lua_unlock(), and if there is no outer handler the \
+     * panic path in luaD_throw() calls lua_unlock() explicitly.  \
+     * Without this re-lock we double-unlock the pthread mutex which \
+     * is undefined behavior and corrupts the mutex on Linux/glibc, \
+     * causing every subsequent lua_lock() on this lua_State to fail \
+     * with EINVAL and abort(). */ \
+    lua_lock((L)); \
     luaD_throw((L), lj.status); \
   } \
 } while(0)