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Recursively locking a SRFI-18 mutex blocks

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* libguile/threads.c (fat_mutex_lock): allow-external-unlock mutexes
  can't be recursive, but a recursive lock attempt can be unblocked by
  an external thread, so these mutexes shouldn't throw an error on
  recursive lock attempts.
* test-suite/tests/srfi-18.test: Add tests.
This commit is contained in:
Andy Wingo 2016-11-05 10:08:01 +01:00
parent b43f11469a
commit f1f68fffb1
2 changed files with 36 additions and 1 deletions
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2
libguile/threads.c
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@ -1152,7 +1152,7 @@ fat_mutex_lock (SCM mutex, scm_t_timespec *timeout, int *ret)
*ret = 1;
break;
}
else if (scm_is_eq (m->owner, new_owner))
else if (scm_is_eq (m->owner, new_owner) && !m->allow_external_unlock)
{
if (m->recursive)
{

35
test-suite/tests/srfi-18.test
View file

@ -302,6 +302,41 @@
(thread-join! t)
(eq? (mutex-state m) 'not-abandoned)))
(pass-if "recursive lock waits"
(let* ((m (make-mutex 'mutex-unlock-2))
(t (make-thread (lambda ()
(mutex-lock! m)
(let ((now (time->seconds (current-time))))
(mutex-lock! m (+ now 0.1)))
(mutex-unlock! m))
'mutex-unlock-2)))
(thread-start! t)
(thread-join! t)
(eq? (mutex-state m) 'not-abandoned)))
(pass-if "recursive lock unblocked by second thread"
(let* ((m1 (make-mutex))
(m2 (make-mutex))
(c (make-condition-variable)))
(mutex-lock! m1)
(let ((t (make-thread (lambda ()
(mutex-lock! m1)
(mutex-lock! m2)
(condition-variable-signal! c)
(mutex-unlock! m1)
(mutex-lock! m2)
(mutex-unlock! m2)))))
(thread-start! t)
(mutex-unlock! m1 c)
;; At this point the thread signalled that it has both m1 and
;; m2, and it will go to try to lock m2 again. We wait for it
;; to block trying to acquire m2 by sleeping a little bit and
;; then unblock it by unlocking m2 from here.
(usleep #e1e5)
(mutex-unlock! m2)
(thread-join! t)
(eq? (mutex-state m2) 'not-abandoned))))
(pass-if "mutex unlock is true when condition is signalled"
(let* ((m (make-mutex 'mutex-unlock-3))
(c (make-condition-variable 'mutex-unlock-3))