Avoid race condition with profiler thread during dispatch table update.

Reported by artemking4. #1460

1 files changed, 11 insertions, 3 deletions

diff --git a/src/lj_dispatch.c b/src/lj_dispatch.c
index 636fb0338..9879a95b9 100644
--- a/src/lj_dispatch.c
+++ b/src/lj_dispatch.c
@@ -103,8 +103,11 @@ void lj_dispatch_init_hotcount(global_State *g)
 #define DISPMODE_PROF   0x40    /* Profiling active. */
 
 /* Update dispatch table depending on various flags. */
-void lj_dispatch_update(global_State *g)
+void LJ_FASTCALL lj_dispatch_update(global_State *g, int nolock)
 {
+#if LJ_HASPROFILE && !LJ_PROFILE_SIGPROF
+  int profile_locked = nolock ? 0 : lj_profile_lock();
+#endif
   uint8_t oldmode = g->dispatchmode;
   uint8_t mode = 0;
 #if LJ_HASJIT
@@ -208,6 +211,11 @@ void lj_dispatch_update(global_State *g)
       lj_dispatch_init_hotcount(g);
 #endif
   }
+#if LJ_HASPROFILE && !LJ_PROFILE_SIGPROF
+  if (profile_locked) lj_profile_unlock();
+#else
+  UNUSED(nolock);
+#endif
 }
 
 /* -- JIT mode setting ---------------------------------------------------- */
@@ -260,7 +268,7 @@ int luaJIT_setmode(lua_State *L, int idx, int mode)
         G2J(g)->flags &= ~(uint32_t)JIT_F_ON;
       else
         G2J(g)->flags |= (uint32_t)JIT_F_ON;
-      lj_dispatch_update(g);
+      lj_dispatch_update(g, 0);
     }
     break;
   case LUAJIT_MODE_FUNC:
@@ -335,7 +343,7 @@ LUA_API int lua_sethook(lua_State *L, lua_Hook func, int mask, int count)
   g->hookcount = g->hookcstart = (int32_t)count;
   g->hookmask = (uint8_t)((g->hookmask & ~HOOK_EVENTMASK) | mask);
   lj_trace_abort(g);  /* Abort recording on any hook change. */
-  lj_dispatch_update(g);
+  lj_dispatch_update(g, 0);
   return 1;
 }