From mboxrd@z Thu Jan 1 00:00:00 1970 From: Qiang Huang Subject: [PATCH] sched: don't clear PF_THREAD_BOUND in select_fallback_rq Date: Thu, 25 Apr 2013 17:01:18 +0800 Message-ID: <5178F0DE.8030808@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Cc: linux-rt-users , Li Zefan , zhangwei To: Steven Rostedt , Thomas Gleixner Return-path: Received: from szxga02-in.huawei.com ([119.145.14.65]:17978 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751436Ab3DYJBv (ORCPT ); Thu, 25 Apr 2013 05:01:51 -0400 Sender: linux-rt-users-owner@vger.kernel.org List-ID: This is revert of "sched-clear-pf-thread-bound-on-fallback-rq.patch" (commit 0d939066acdcb in v3.4-rt),. Select_fallback_rq() can be easilly called during system boot, because select_task_rq_fair() just return task_cpu(p) for bounded kernel threads, which is 0 during system boot and not in tsk_cpus_allowed, so select_fallback_rq() is called and PF_THREAD_BOUND is cleared. In my box, 1/3 bounded kernel threads will clear that flag after boot. And it will cause problems, for example: # for pid in `ps -e -o pid`; do taskset -p -c 0-15 $pid; done this command will cause system hung. What's more, I don't see why we need to clear this flag any more, because "cpu/rt: Rework cpu down for PREEMPT_RT" already remove the optimization for PF_THREAD_BOUND on migrate_disable/enable. Signed-off-by: Qiang Huang --- kernel/sched/core.c | 6 ------ 1 files changed, 0 insertions(+), 6 deletions(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 751ec60..8db6e3b 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1327,12 +1327,6 @@ out: } } - /* - * Clear PF_THREAD_BOUND, otherwise we wreckage - * migrate_disable/enable. See optimization for - * PF_THREAD_BOUND tasks there. - */ - p->flags &= ~PF_THREAD_BOUND; return dest_cpu; } -- 1.7.1