Re: Bug with coroutines?
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- Subject: Re: Bug with coroutines?
- From: Sean Conner <sean@...>
- Date: 2014年6月12日 17:13:51 -0400
It was thus said that the Great Thiago L. once stated:
>
> On 12/06/2014 17:53, Andrew Starks wrote:
>
> >In both cases, the main Lua state is closed/ interrupted. The
> >coroutine never receives the signal because in order for that to
> >happen, the main Lua state would need to pass it off to that thread.
> >Instead, it simply closes, which means that the thread is collected,
> >but the return value is never read or processed.
> >
> >I can say with a pretty good level of certainty that it's not a bug,
> >unless you think that Lua should pass EINTR to its coroutine, but
> >given that it's not an OS thread, that would be weird.
> >
> >
> >-Andrew
> Well it should keep track of the active coroutine at least...
Well, the code in question, from lua.c:
static void lstop (lua_State *L, lua_Debug *ar) {
(void)ar; /* unused arg. */
lua_sethook(L, NULL, 0, 0);
luaL_error(L, "interrupted!");
}
static void laction (int i) {
signal(i, SIG_DFL); /* if another SIGINT happens before lstop,
terminate process (default action) */
lua_sethook(globalL, lstop, LUA_MASKCALL | LUA_MASKRET | LUA_MASKCOUNT,1);
}
/* ... */
static int docall (lua_State *L, int narg, int clear) {
int status;
int base = lua_gettop(L) - narg; /* function index */
lua_pushcfunction(L, traceback); /* push traceback function */
lua_insert(L, base); /* put it under chunk and args */
signal(SIGINT, laction);
status = lua_pcall(L, narg, (clear ? 0 : LUA_MULTRET), base);
signal(SIGINT, SIG_DFL);
lua_remove(L, base); /* remove traceback function */
/* force a complete garbage collection in case of errors */
if (status != 0) lua_gc(L, LUA_GCCOLLECT, 0);
return status;
}
/* ... */
To me, it looks like a wierd interaction between lua_pcall() and
coroutines. When I run the test code, ^C once does nothing; ^C twice takes
me back to the Unix prompt.
I'm also surprised that lua_sethook() is thread safe. Frankly, I've been
bitten by calling C functions from signal handlers (one of the toughest bugs
I've had to track down was due to calling functions from a signal handler)
so I'm surprised this works.
-spc