Re: [Chicken-hackers] Regarding #1564: srfi-18: (mutex-unlock) Internal scheduler error

[Jörg F . Wittenberger]

Hello Megane,

On Nov 30 2018, megane wrote:

> Hi,
>
> Here's another version that crashes quickly with "very high
> probability".
...
>    24   Error: (mutex-unlock) Internal scheduler error: unknown thread state
>    25   #<thread: thread1>
>    26   ready

This bears an uncanny resemblance to scheduler issues I've been fighting a 
long ago.

Too long to ago.

> --- A fix
>
> Just allow the 'ready state for threads in mutex-unlock!
>
> ...
> Is this a correct fix?


Too long ago.

But it feels wrong. We'd rather make sure there is no ready thread in the 
queue waiting for a mutex in the first place.

Diffing the changes I maintained quite a while back 
http://ball.askemos.org/Ad60e3fb123a79b2e5128915116b288f7/chicken-4.9.1-ball.tar.gz 
you will find that I added a

##sys#thread-clear-blocking-state!

Towards the end of scheduler.scm and used it for consistency whereever I 
ran into not-so-clean unlocks.

Now this is still an invasive change. But looking at the source of 
scheduler and srfi-18 in chicken 5 right now, I can't fight the feeling 
that it is working around the missing changes at several places.

Best

/Jörg