Re: OpenMCL 1.0 timed-wait-on-semaphore not timing out

TIMED-WAIT-ON-SEMAPHORE uses GET-INTERNAL-REAL-TIME to determine
when the timeout should expire.

Ordinarily, it just blocks waiting on the semaphore.  If it obtains
the semaphore or if the wait times out, it returs correctly, but
if the blocking wait is interrupted (the GC can cause this), it
inconsistently and incorrectly uses GET-INTERNAL-RUN-TIME and
compares the result to the result obtained from GET-INTERNAL-REAL-TIME
earlier.   This is almost always completely wrong, and could explain
the symptoms that you report.

(Prior to 1.0, the calculation of elapsed time after an interrupt
happened in C code in the lisp kernel; it was presumably correct,
but, since C code is generally uninterruptible, a long wait couldn't
be aborted via PROCESS-INTERRUPT or ^C.)

On Fri, 27 Jan 2006, Lennart Staflin wrote:

> Hi,
> I have run into an occasional problem with timed-wait-on-semaphore.
> This is a problem in 1.0 in 0.14 it worked well. It seems that
> occasionally timed-wait-on-semaphore will hang or take much longer to
> time out then is should.
>
> Test case below, it should print something every 5 minutes. When I run
> it it seldom gets past 40 iterations usually it hangs earlier. The
> machine is an iBook. At first I thought the sleep had something to do
> with the hang. But I observe the hang even when on external power (and
> it usually don't sleep then). Testing this takes time and I'm not at
> the machine all the time, i can't be 100% sure if my observations are
> accurate. (Hmm, I wonder if using a shorter timeout will trigger the
> hang earlier.)
>
> //Lennart Staflin
>
>
> (in-package :cl-user)
>
>
> (defvar *sem* (make-semaphore))
>
>
> (defun format-date (date &optional include-time)
>   (if date
>       (multiple-value-bind (second minute hour date month year)
>           (decode-universal-time date)
>         (if include-time
>             (format nil "~d-~2,'0d-~2,'0d ~2,'0d:~2,'0d:~2,'0d"
>                     year month date hour minute second)
>             (format nil "~d-~2,'0d-~2,'0d" year month date)))
>       "--"))
>
>
> (defun format-time (universal-time) (format-date universal-time t))
>
>
> (defun test-bug-1 ()
>   (loop for i from 1 to 1000
>      do (progn (format t "~A Looping ~A~%"
>                        (format-time (get-universal-time))
>                        i)
>                (force-output)
>                (timed-wait-on-semaphore *sem* 300)))  )
>
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