Re: When must I provide a self-defined lua_lock macro(e.g: #define lua_lock(L) pthread_lock(&mutex))?

[孙世龙 sunshilong <sunshilong369@...>]

>Let's say you call a lua function, this locked lua state and now nothing can unlock it unless the functions finishes. if that infinite loop calls a C function or >triggers any lua api they call lock function again which lock make it wait itself
>If you want multithreading try something like https://github.com/effil/eiffel
Do you have any idea about how eiffel avoid the deadlocks?
Can I draw the conclusion that the eiffel drops some lock and unlock
operation (comparing to vanilla Lua) to avoid deadlocks?

On Thu, Jan 28, 2021 at 7:40 PM Spar <developspartv@gmail.com> wrote:
>
> If you want multithreading try something like https://github.com/effil/effil
> On 28 Jan 2021, 14:35 +0300, 孙世龙 sunshilong <sunshilong369@gmail.com>, wrote:
>
> Spar > Any infinite loop in lua code will lock your mutex forever
> I am shocked to hear that indeed.
> How come it is? Once there is a lua_lock, there will be a lua_unlock.
> Could you please give me a simple example？
>
> On Thu, Jan 28, 2021 at 7:30 PM Spar <developspartv@gmail.com> wrote:
>
>
> Any infinite loop in lua code will lock your mutex forever
> On 28 Jan 2021, 14:28 +0300, 孙世龙 sunshilong <sunshilong369@gmail.com>, wrote:
>
> But providing lua_lock you will get a multithreaded Lua very difficult to use, there will be deadlock problems difficult to solve.
>
> Did you ever encounter deadlock problems when using vanilla Lua?
>
> Best regards
> sunshilong
>
> On Thu, Jan 28, 2021 at 6:22 PM Victor Bombi <sonoro@telefonica.net> wrote:
>
>
>
> On January 28, 2021 at 10:17 AM 孙世龙 sunshilong <sunshilong369@gmail.com> wrote:
>
>
> Hi, list
>
> In general, the macro named lua_lock is expanded as a
> no-operation(i.e (void)0).
>
> Here is the related code snippet in Lua-5.3.5：
> /*
> ** macros that are executed whenever program enters the Lua core
> ** ('lua_lock') and leaves the core ('lua_unlock')
> */
> #if !defined(lua_lock)
> #define lua_lock(L) ((void) 0)
> #define lua_unlock(L) ((void) 0)
> #endif
> I wonder when I need to provide a self-defined macro (e.g:
> #define lua_lock(L) pthread_lock(&mutex))?
>
> I would appreciate it if you could shed some light on this question.
>
> Best regards
>
>
> Lua is not multithread ready unless you define lua_lock. But providing lua_lock you will get a multithreaded Lua very difficult to use, there will be deadlock problems difficult to solve.
> The best way to use Lua in a multithread environment is to create a different lua_State in each thread and let all different lua_States to inter-communicate. I would recomend using LuaLanes for achieving this althought there are a lot of alternatives.
>
> Best
> Victor Bombí
>
> sunshilong