From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753290AbdCQDpu (ORCPT ); Thu, 16 Mar 2017 23:45:50 -0400 Received: from mail-pf0-f196.google.com ([209.85.192.196]:32892 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753108AbdCQDps (ORCPT ); Thu, 16 Mar 2017 23:45:48 -0400 From: Wanpeng Li X-Google-Original-From: Wanpeng Li To: linux-kernel@vger.kernel.org Cc: Ingo Molnar , Peter Zijlstra , Wanpeng Li , Mike Galbraith , Thomas Gleixner Subject: [PATCH] sched/core: Fix rq lock pinning warning after call balance callbacks Date: Thu, 16 Mar 2017 19:45:19 -0700 Message-Id: <1489718719-3951-1-git-send-email-wanpeng.li@hotmail.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wanpeng Li This can be reproduced by running rt-migrate-test: WARNING: CPU: 2 PID: 2195 at kernel/locking/lockdep.c:3670 lock_unpin_lock+0x172/0x180 unpinning an unpinned lock CPU: 2 PID: 2195 Comm: rt-migrate-test Tainted: G W 4.11.0-rc2+ #1 Call Trace: dump_stack+0x85/0xc2 __warn+0xcb/0xf0 warn_slowpath_fmt+0x5f/0x80 lock_unpin_lock+0x172/0x180 __balance_callback+0x75/0x90 __schedule+0x83f/0xc00 ? futex_wait_setup+0x82/0x130 schedule+0x3d/0x90 futex_wait_queue_me+0xd4/0x170 futex_wait+0x119/0x260 ? __lock_acquire+0x4c8/0x1900 ? stop_one_cpu+0x94/0xc0 do_futex+0x2fe/0xc10 ? sched_setaffinity+0x1c1/0x290 SyS_futex+0x81/0x190 ? rcu_read_lock_sched_held+0x72/0x80 do_syscall_64+0x73/0x1f0 entry_SYSCALL64_slow_path+0x25/0x25 We utilize balance callbacks to delay the load-balancing operations {rt,dl}*{push,pull} until we've done all the important work. The push/pull operations can unlock/lock the current rq for safety acquires the src's and dest's rq->locks in a fair way. It's safe to drop the rq lock here, unpin and repin to avoid the splat. Reported-by: Fengguang Wu Cc: Mike Galbraith Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Wanpeng Li --- kernel/sched/core.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index c762f62..cd901f6 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2787,7 +2787,9 @@ static void __balance_callback(struct rq *rq) head->next = NULL; head = next; + rq_unpin_lock(rq, &rf); func(rq); + rq_repin_lock(rq, &rf); } rq_unlock_irqrestore(rq, &rf); } -- 2.7.4