[src/trunk]: src/tests/lib/libc/sys Fix race in t_ptrace_wait* LWP tests

[kamil <kamil%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/c19e0a3222d7
branches:  trunk
changeset: 455294:c19e0a3222d7
user:      kamil <kamil%NetBSD.org@localhost>
date:      Sun Oct 13 09:42:15 2019 +0000

description:
Fix race in t_ptrace_wait* LWP tests

Increment the done variable under a mutex. This variable was updated
non-atomically and sometimes not reaching the expected treshold.

diffstat:

 tests/lib/libc/sys/t_ptrace_wait.c |  7 +++++--
 1 files changed, 5 insertions(+), 2 deletions(-)

diffs (34 lines):

diff -r ae593ad29862 -r c19e0a3222d7 tests/lib/libc/sys/t_ptrace_wait.c
--- a/tests/lib/libc/sys/t_ptrace_wait.c        Sun Oct 13 07:46:16 2019 +0000
+++ b/tests/lib/libc/sys/t_ptrace_wait.c        Sun Oct 13 09:42:15 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: t_ptrace_wait.c,v 1.136 2019/10/13 04:05:39 kamil Exp $        */
+/*     $NetBSD: t_ptrace_wait.c,v 1.137 2019/10/13 09:42:15 kamil Exp $        */
 
 /*-
  * Copyright (c) 2016, 2017, 2018, 2019 The NetBSD Foundation, Inc.
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__RCSID("$NetBSD: t_ptrace_wait.c,v 1.136 2019/10/13 04:05:39 kamil Exp $");
+__RCSID("$NetBSD: t_ptrace_wait.c,v 1.137 2019/10/13 09:42:15 kamil Exp $");
 
 #include <sys/param.h>
 #include <sys/types.h>
@@ -5458,12 +5458,15 @@
 #define TRACE_THREADS_NUM 100
 
 static volatile int done;
+pthread_mutex_t trace_threads_mtx = PTHREAD_MUTEX_INITIALIZER;
 
 static void *
 trace_threads_cb(void *arg __unused)
 {
 
+       pthread_mutex_lock(&trace_threads_mtx);
        done++;
+       pthread_mutex_unlock(&trace_threads_mtx);
 
        while (done < TRACE_THREADS_NUM)
                sched_yield();