new method thread:interrupt()

[osch]

Hi,

here comes a method to interrupt a thread using a debug hook similiar to the SIGINT signal handler of the original lua interpreter (see function laction in lua.c).

Best regards,
Oliver

[moteus]

This is not valid access to LuaState from different thread while it executes insepareate thread

[osch]

But lua_sethook is called from a signal handler in the original lua interpreter and special care has been taken to make the function lua_sethook asynchronously callable, see also the documentation from ldebug.c:

/*
** This function can be called asynchronously (e.g. during a signal).
** Fields 'oldpc', 'basehookcount', and 'hookcount' (set by
** 'resethookcount') are for debug only, and it is no problem if they
** get arbitrary values (causes at most one wrong hook call). 'hookmask'
** is an atomic value. We assume that pointers are atomic too (e.g., gcc
** ensures that for all platforms where it runs). Moreover, 'hook' is
** always checked before being called (see 'luaD_hook').
*/
LUA_API void lua_sethook (lua_State *L, lua_Hook func, int mask, int count) {

[moteus]

Did not know that. Thanks.
May be you can also add simple test case.
I think this is how it shold work.

local llthreads = require"llthreads"
local utils     = require "utils"
local sleep     = utils.sleep

local include = utils.thread_init .. [[
local llthreads = require"llthreads"
local sleep = require "utils".sleep
]]

local thread = llthreads.new(include .. [[
  for i = 1, 10 do sleep(1) end
  os.exit(-1)
]])

thread:start()
sleep(1)
thread:interrupt()

local ok, err = thread:join()
print("thread:join(): ", ok, err)
assert(ok, err)
print("Done!")

[osch]

OK, I will look into the test cases tomorrow.

[osch]

OK, I added the test cases and they ran successfully on travis and appveyor.

[moteus]

Sorry for late response.
I like this feature. I have only one concern.
Error string should be part of public api and i do not like
exclamination mark in it.
Also may be add library name as prefix or at least thread:: prefix?

[osch]

No problems, I just committed some changes trying to incorporate your wishes: the interrupeted message contains no exclamation mark (btw. the message "interrupted!" is the original message from the lua interpreter, see lstop in lua.c), the message contains now the module name as prefix and is also available in the public api as interrupted_error.