Re: deadlock in scm_join_thread(_timed)

[Neil Jerram <neil@ossau.uklinux.net>]

"Julian Graham" <joolean@gmail.com> writes:

> Hi Neil,
>
>> Based on the synopsis above, I agree that moving step 1 inside the loop
>> should fix this.  In addition, though, I think it would be very good if we
>> could add a minimal test that currently reproduces the deadlock, and so will
>> serve to guard against future regressions here.  Do you have such a test?
>
> I don't -- it seems to be pretty dependent on timing.  I noticed it
> while running my SRFI-18 test suite in a loop, and it took hours to
> trigger.  Any suggestions?

I'm looking into this now.  Here's a nice little program that
reproduces the deadlock.

(use-modules (ice-9 threads))

(define other-thread
  (make-thread sleep 5))

(letrec ((delay-count 10)
	 (aproc (lambda ()
		  (display delay-count) (newline)
		  (set! delay-count (- delay-count 1))
		  (if (zero? delay-count)
		      (begin
			(display "sleeping...\n")
			(sleep 10)
			(display "waking...\n"))
		      (system-async-mark aproc)))))
  (sleep 2)
  (system-async-mark aproc)
  (join-thread other-thread))


Regards,
        Neil