* [PATCH 2/2] pthread: implement try/timed join variants
2015-09-28 21:58 [PATCH 1/2] pthread: add missing memory barrier Bobby Bingham
@ 2015-09-28 21:58 ` Bobby Bingham
2015-09-28 22:21 ` [PATCH 1/2] pthread: add missing memory barrier Rich Felker
1 sibling, 0 replies; 3+ messages in thread
From: Bobby Bingham @ 2015-09-28 21:58 UTC (permalink / raw)
To: musl
---
include/pthread.h | 2 ++
src/thread/pthread_join.c | 34 +++++++++++++++++++++++++++-------
2 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/include/pthread.h b/include/pthread.h
index af70b73..3d2e0c4 100644
--- a/include/pthread.h
+++ b/include/pthread.h
@@ -214,6 +214,8 @@ struct cpu_set_t;
int pthread_getaffinity_np(pthread_t, size_t, struct cpu_set_t *);
int pthread_setaffinity_np(pthread_t, size_t, const struct cpu_set_t *);
int pthread_getattr_np(pthread_t, pthread_attr_t *);
+int pthread_tryjoin_np(pthread_t, void **);
+int pthread_timedjoin_np(pthread_t, void **, const struct timespec *);
#endif
#ifdef __cplusplus
diff --git a/src/thread/pthread_join.c b/src/thread/pthread_join.c
index eb78e2f..9c3be08 100644
--- a/src/thread/pthread_join.c
+++ b/src/thread/pthread_join.c
@@ -5,19 +5,39 @@ int __munmap(void *, size_t);
void __pthread_testcancel(void);
int __pthread_setcancelstate(int, int *);
-int __pthread_join(pthread_t t, void **res)
+static int reclaim(pthread_t t, void **res)
{
- int tmp, cs;
+ if (res) *res = t->result;
+ if (t->map_base) __munmap(t->map_base, t->map_size);
+ return 0;
+}
+
+int __pthread_tryjoin_np(pthread_t t, void **res)
+{
+ if (t->tid) return EBUSY;
+ a_barrier();
+ return reclaim(t, res);
+}
+
+int __pthread_timedjoin_np(pthread_t t, void **res, const struct timespec *at)
+{
+ int tmp, cs, r = 0;
__pthread_testcancel();
__pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
if (cs == PTHREAD_CANCEL_ENABLE) __pthread_setcancelstate(cs, 0);
if (!(tmp = t->tid)) a_barrier();
- else do __timedwait_cp(&t->tid, tmp, 0, 0, 0);
- while ((tmp = t->tid));
+ else do r = __timedwait_cp(&t->tid, tmp, CLOCK_REALTIME, at, 0);
+ while ((tmp = t->tid) && r != ETIMEDOUT && r != EINVAL);
__pthread_setcancelstate(cs, 0);
- if (res) *res = t->result;
- if (t->map_base) __munmap(t->map_base, t->map_size);
- return 0;
+ if (r == ETIMEDOUT || r == EINVAL) return r;
+ return reclaim(t, res);
+}
+
+int __pthread_join(pthread_t t, void **res)
+{
+ return __pthread_timedjoin_np(t, res, 0);
}
+weak_alias(__pthread_tryjoin_np, pthread_tryjoin_np);
+weak_alias(__pthread_timedjoin_np, pthread_timedjoin_np);
weak_alias(__pthread_join, pthread_join);
--
2.5.3
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH 1/2] pthread: add missing memory barrier
2015-09-28 21:58 [PATCH 1/2] pthread: add missing memory barrier Bobby Bingham
2015-09-28 21:58 ` [PATCH 2/2] pthread: implement try/timed join variants Bobby Bingham
@ 2015-09-28 22:21 ` Rich Felker
1 sibling, 0 replies; 3+ messages in thread
From: Rich Felker @ 2015-09-28 22:21 UTC (permalink / raw)
To: musl
On Mon, Sep 28, 2015 at 04:58:44PM -0500, Bobby Bingham wrote:
> posix requires pthread_join to synchronize memory on success. in the
> case that we call __timedwait_cp, we can rely on its futex_wake call
> to synchronize memory, but we need a memory barrier for the case where
> we don't call it.
> ---
> src/thread/pthread_join.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/src/thread/pthread_join.c b/src/thread/pthread_join.c
> index 966b4ab..eb78e2f 100644
> --- a/src/thread/pthread_join.c
> +++ b/src/thread/pthread_join.c
> @@ -11,7 +11,9 @@ int __pthread_join(pthread_t t, void **res)
> __pthread_testcancel();
> __pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cs);
> if (cs == PTHREAD_CANCEL_ENABLE) __pthread_setcancelstate(cs, 0);
> - while ((tmp = t->tid)) __timedwait_cp(&t->tid, tmp, 0, 0, 0);
> + if (!(tmp = t->tid)) a_barrier();
> + else do __timedwait_cp(&t->tid, tmp, 0, 0, 0);
> + while ((tmp = t->tid));
> __pthread_setcancelstate(cs, 0);
> if (res) *res = t->result;
> if (t->map_base) __munmap(t->map_base, t->map_size);
> --
I think this works, but it depends on __timedwait_cp containing a
barrier. Is this something we should view as part of its contract or
as an implementation detail? We could punt on the question and just
put an unconditional a_barrier() after the loop above, but I'd kind of
like to think through the question while we're looking at it.
Rich
^ permalink raw reply [flat|nested] 3+ messages in thread