From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from sfi-mx-1.v28.ch3.sourceforge.com ([172.29.28.121] helo=mx.sourceforge.net) by sfs-ml-4.v29.ch3.sourceforge.com with esmtp (Exim 4.69) (envelope-from ) id 1NaaDR-0000sX-4Z for ltp-list@lists.sourceforge.net; Thu, 28 Jan 2010 19:39:45 +0000 Received: from e7.ny.us.ibm.com ([32.97.182.137]) by sfi-mx-1.v28.ch3.sourceforge.com with esmtps (TLSv1:AES256-SHA:256) (Exim 4.69) id 1NaaDQ-0005yn-A5 for ltp-list@lists.sourceforge.net; Thu, 28 Jan 2010 19:39:45 +0000 Received: from d01relay06.pok.ibm.com (d01relay06.pok.ibm.com [9.56.227.116]) by e7.ny.us.ibm.com (8.14.3/8.13.1) with ESMTP id o0SJWwno030986 for ; Thu, 28 Jan 2010 14:32:58 -0500 Received: from d01av01.pok.ibm.com (d01av01.pok.ibm.com [9.56.224.215]) by d01relay06.pok.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o0SJdbxd1659134 for ; Thu, 28 Jan 2010 14:39:37 -0500 Received: from d01av01.pok.ibm.com (loopback [127.0.0.1]) by d01av01.pok.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o0SJdbli022528 for ; Thu, 28 Jan 2010 14:39:37 -0500 Message-ID: <4B61E7F7.3000502@us.ibm.com> Date: Thu, 28 Jan 2010 11:39:35 -0800 From: Darren Hart MIME-Version: 1.0 Subject: [LTP] [PATCH] prio-wake: avoid glibc to kernel sleep race List-Id: Linux Test Project General Discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: ltp-list-bounces@lists.sourceforge.net To: ltp-list prio-wake: avoid glibc to kernel sleep race In the unlocked broadcast scenario, there exists a race between when the running_threads variable reaches rt_threads and when the last worker_thread blocks in the kernel after a cond_wait(). It is possible for a thread to miss the broadcast if it fails to sleep before the broadcast is issued. The previous code did not guarantee a small window of time to allow the threads to get to sleep. It also used an unreasonably large sleep time which unnecessarily extended the length of the test run time. This patch ensures some time is given to the threads to get to sleep and at the same time uses a much shorter (1000x) sleep period which results in a 50-100x reduction in test run time. Lastly, two unecessary loops waiting for the threads to complete were removed, relying on pthread_join() instead to wait for the threads to complete. Signed-off-by: Darren Hart Acked-by: Will Schmidt --- func/prio-wake/prio-wake.c | 10 ++++------ 1 file changed, 4 insertions(+), 6 deletions(-) Index: realtime/func/prio-wake/prio-wake.c =================================================================== --- realtime.orig/func/prio-wake/prio-wake.c +++ realtime/func/prio-wake/prio-wake.c @@ -108,7 +108,10 @@ void *master_thread(void* arg) /* make sure children are started */ while (running_threads < rt_threads) - sleep(1); + usleep(1000); + /* give the worker threads a chance to get to sleep in the kernel + * in the unlocked broadcast case. */ + usleep(1000); start = rt_gettime() - beginrun; @@ -120,8 +123,6 @@ void *master_thread(void* arg) if (locked_broadcast) rc = pthread_mutex_unlock(&mutex); - while (running_threads > 0) - sleep(1); return NULL; } @@ -157,9 +158,6 @@ void *worker_thread(void* arg) rc = pthread_mutex_unlock(&mutex); - /* wait for all threads to quit */ - while (running_threads > 0) - sleep(1); return NULL; } -- Darren Hart IBM Linux Technology Center Real-Time Linux Team ------------------------------------------------------------------------------ The Planet: dedicated and managed hosting, cloud storage, colocation Stay online with enterprise data centers and the best network in the business Choose flexible plans and management services without long-term contracts Personal 24x7 support from experience hosting pros just a phone call away. http://p.sf.net/sfu/theplanet-com _______________________________________________ Ltp-list mailing list Ltp-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ltp-list