Re: Thread issues

[Vladimir T. <vtz...@gm...>]

On 7/11/09, Tobias C. Rittweiler <tc...@fr...> wrote:
>
> I tried to use the new thread interface in Clisp's SWANK backend, and I
> have come across a few minor issues, and one serious bug:
>
>   * The lock-related functions are consistently called MUTEX-foo, but
>     the macro to grab a mutex is called WITH-LOCK.

Does with-mutex-lock sound better? Sam?

>   * I don't like that (thread-name (make-thread #'(lambda ()))) returns
>     #<UNBOUND>, as you cannot use (or (thread-name ...) "SOME-DEFAULT")
>     this way.

Why don't you name the thread? I think :name should be mandatory -
like for make-mutex and make-exemption. This helps debugging and does
not annoy too much.

>   * I think the default print-object method specializing on threads
>     should print whether the thread is currently running, or has been
>     stopped.

While it may be useful for quick check - there is thread-active-p for
this purpose. (notice that current state of thread (running or
finished) may change while you read it - do not rely on it- it is just
for debugging).

> Now to a much more serious issue:
>
>   * If I run the file below, clisp exits with "Aborted". I'm on
>     Linux-x86/32, compiled clisp from CVS four hours ago. Have threads
>     and weak-hashtables been tested?

Thanks.
weak-hashtables and threads were not tested together. The problem is
somehow related to:
http://sourceforge.net/tracker/?func=detail&aid=1472478&group_id=1355&atid=101355
While not identical they share quite in common. Threads, mutexes,
exemptions (and finalizers) will cause problems when mixed with weak
pointers.
As for current version of clisp  - do not use them together. I'll work
on fixing this.

Vladimir

> PS.
>
> (defvar *thread-plist-table-lock*
>   (mp:make-mutex :name "THREAD-PLIST-TABLE-LOCK"))
>
> (defvar *thread-plist-table* (make-hash-table :weak :key)
>   "A hashtable mapping threads to a plist.")
>
> (defvar *thread-id-counter* 0)
>
> (defun thread-id (thread)
>   (mp:with-lock (*thread-plist-table-lock*)
>     (or (getf (gethash thread *thread-plist-table*) 'thread-id)
>         (setf (getf (gethash thread *thread-plist-table*) 'thread-id)
>               (incf *thread-id-counter*)))))
>
> (defvar *thread* (make-thread (lambda () (loop (sleep 1)))))
>
> (thread-id *thread*)
>
> (thread-interrupt *thread* :function t)
>
> (setq *thread* nil)
>
> (gc)
>