Only in lua-5.1.1/src: #ldo.c#
diff -ur lua-5.1.1/src/lapi.c lua-5.1.1-copatch/src/lapi.c
--- lua-5.1.1/src/lapi.c	2006-06-07 05:37:17.000000000 -0700
+++ lua-5.1.1-copatch/src/lapi.c	2007-11-25 14:41:23.000000000 -0800
@@ -119,6 +119,7 @@
   for (i = 0; i < n; i++) {
     setobj2s(to, to->top++, from->top + i);
   }
+  to->nresumes = from->nresumes;
   lua_unlock(to);
 }
 
diff -ur lua-5.1.1/src/ldo.c lua-5.1.1-copatch/src/ldo.c
--- lua-5.1.1/src/ldo.c	2006-06-05 12:36:14.000000000 -0700
+++ lua-5.1.1-copatch/src/ldo.c	2007-11-25 14:44:33.000000000 -0800
@@ -8,6 +8,7 @@
 #include <setjmp.h>
 #include <stdlib.h>
 #include <string.h>
+#include <stdio.h>
 
 #define ldo_c
 #define LUA_CORE
@@ -367,16 +368,17 @@
 ** function position.
 */ 
 void luaD_call (lua_State *L, StkId func, int nResults) {
-  if (++L->nCcalls >= LUAI_MAXCCALLS) {
-    if (L->nCcalls == LUAI_MAXCCALLS)
+    int effCalls = ++L->nCcalls + L->nresumes;
+    if (effCalls >= LUAI_MAXCCALLS) {
+    if (effCalls == LUAI_MAXCCALLS)
       luaG_runerror(L, "C stack overflow");
-    else if (L->nCcalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
-      luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
-  }
-  if (luaD_precall(L, func, nResults) == PCRLUA)  /* is a Lua function? */
-    luaV_execute(L, 1);  /* call it */
-  L->nCcalls--;
-  luaC_checkGC(L);
+    else if (effCalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
+	luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
+    }
+    if (luaD_precall(L, func, nResults) == PCRLUA)  /* is a Lua function? */
+	luaV_execute(L, 1);  /* call it */
+    L->nCcalls--;
+    luaC_checkGC(L);
 }
 
 
@@ -401,7 +403,15 @@
     else  /* yielded inside a hook: just continue its execution */
       L->base = L->ci->base;
   }
+  int effCalls = L->nCcalls + ++L->nresumes;
+  if (effCalls >= LUAI_MAXCCALLS) {
+      if (effCalls == LUAI_MAXCCALLS)
+	  luaG_runerror(L, "C stack overflow");
+      else if (effCalls >= (LUAI_MAXCCALLS + (LUAI_MAXCCALLS>>3)))
+	  luaD_throw(L, LUA_ERRERR);  /* error while handing stack error */
+  }
   luaV_execute(L, cast_int(L->ci - L->base_ci));
+  --L->nresumes;
 }
 
 
@@ -454,6 +464,7 @@
                 ptrdiff_t old_top, ptrdiff_t ef) {
   int status;
   unsigned short oldnCcalls = L->nCcalls;
+  unsigned short oldnresumes = L->nresumes;
   ptrdiff_t old_ci = saveci(L, L->ci);
   lu_byte old_allowhooks = L->allowhook;
   ptrdiff_t old_errfunc = L->errfunc;
@@ -464,6 +475,7 @@
     luaF_close(L, oldtop);  /* close eventual pending closures */
     luaD_seterrorobj(L, status, oldtop);
     L->nCcalls = oldnCcalls;
+    L->nresumes = oldnresumes;
     L->ci = restoreci(L, old_ci);
     L->base = L->ci->base;
     L->savedpc = L->ci->savedpc;
diff -ur lua-5.1.1/src/lstate.c lua-5.1.1-copatch/src/lstate.c
--- lua-5.1.1/src/lstate.c	2006-05-24 07:15:50.000000000 -0700
+++ lua-5.1.1-copatch/src/lstate.c	2007-11-25 14:30:43.000000000 -0800
@@ -94,6 +94,7 @@
   L->openupval = NULL;
   L->size_ci = 0;
   L->nCcalls = 0;
+  L->nresumes = 0;
   L->status = 0;
   L->base_ci = L->ci = NULL;
   L->savedpc = NULL;
@@ -206,6 +207,7 @@
     L->ci = L->base_ci;
     L->base = L->top = L->ci->base;
     L->nCcalls = 0;
+    L->nresumes = 0;
   } while (luaD_rawrunprotected(L, callallgcTM, NULL) != 0);
   lua_assert(G(L)->tmudata == NULL);
   luai_userstateclose(L);
diff -ur lua-5.1.1/src/lstate.h lua-5.1.1-copatch/src/lstate.h
--- lua-5.1.1/src/lstate.h	2006-02-06 10:27:59.000000000 -0800
+++ lua-5.1.1-copatch/src/lstate.h	2007-11-25 14:30:15.000000000 -0800
@@ -112,6 +112,7 @@
   int stacksize;
   int size_ci;  /* size of array `base_ci' */
   unsigned short nCcalls;  /* number of nested C calls */
+  unsigned short nresumes;  /* number of coroutine resumes */
   lu_byte hookmask;
   lu_byte allowhook;
   int basehookcount;