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-rw-r--r--libguile/async.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/libguile/async.c b/libguile/async.c
index bd840762f..e10bc562b 100644
--- a/libguile/async.c
+++ b/libguile/async.c
@@ -1,4 +1,4 @@
-/* Copyright 1995-1998,2000-2002,2004,2006,2008-2011,2014,2018
+/* Copyright 1995-1998,2000-2002,2004,2006,2008-2011,2014,2018-2019
Free Software Foundation, Inc.
This file is part of Guile.
@@ -86,7 +86,7 @@ scm_i_async_push (scm_thread *t, SCM proc)
disable that newly-severed tail by setting its cdr to #f. Not so
nice, but oh well. */
asyncs = scm_atomic_ref_scm (&t->pending_asyncs);
- do
+ while (1)
{
/* Traverse the asyncs list atomically. */
SCM walk;
@@ -95,9 +95,13 @@ scm_i_async_push (scm_thread *t, SCM proc)
walk = scm_atomic_ref_scm (SCM_CDRLOC (walk)))
if (scm_is_eq (SCM_CAR (walk), proc))
return;
+
+ SCM expected = asyncs;
+ asyncs = scm_atomic_compare_and_swap_scm
+ (&t->pending_asyncs, asyncs, scm_cons (proc, asyncs));
+ if (scm_is_eq (asyncs, expected))
+ return;
}
- while (!scm_atomic_compare_and_swap_scm (&t->pending_asyncs, &asyncs,
- scm_cons (proc, asyncs)));
}
/* Precondition: there are pending asyncs. */
@@ -123,8 +127,9 @@ scm_i_async_pop (scm_thread *t)
/* Sever the tail. */
if (scm_is_false (penultimate_pair))
{
- if (!scm_atomic_compare_and_swap_scm (&t->pending_asyncs, &asyncs,
- SCM_EOL))
+ if (!scm_is_eq (asyncs,
+ scm_atomic_compare_and_swap_scm (&t->pending_asyncs,
+ asyncs, SCM_EOL)))
continue;
}
else