From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 83A19C06510 for ; Tue, 2 Jul 2019 16:49:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 572BA20989 for ; Tue, 2 Jul 2019 16:49:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727054AbfGBQtf (ORCPT ); Tue, 2 Jul 2019 12:49:35 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:4910 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726150AbfGBQte (ORCPT ); Tue, 2 Jul 2019 12:49:34 -0400 Received: from pps.filterd (m0098414.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.27/8.16.0.27) with SMTP id x62GivX8060400; Tue, 2 Jul 2019 12:49:26 -0400 Received: from ppma01wdc.us.ibm.com (fd.55.37a9.ip4.static.sl-reverse.com [169.55.85.253]) by mx0b-001b2d01.pphosted.com with ESMTP id 2tgary8u67-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 02 Jul 2019 12:49:26 -0400 Received: from pps.filterd (ppma01wdc.us.ibm.com [127.0.0.1]) by ppma01wdc.us.ibm.com (8.16.0.27/8.16.0.27) with SMTP id x62GijE1005469; Tue, 2 Jul 2019 16:49:25 GMT Received: from b01cxnp23032.gho.pok.ibm.com (b01cxnp23032.gho.pok.ibm.com [9.57.198.27]) by ppma01wdc.us.ibm.com with ESMTP id 2tdym6qdpj-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=NOT); Tue, 02 Jul 2019 16:49:25 +0000 Received: from b01ledav003.gho.pok.ibm.com (b01ledav003.gho.pok.ibm.com [9.57.199.108]) by b01cxnp23032.gho.pok.ibm.com (8.14.9/8.14.9/NCO v10.0) with ESMTP id x62GnOmL22479290 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 2 Jul 2019 16:49:25 GMT Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id E2E32B2064; Tue, 2 Jul 2019 16:49:24 +0000 (GMT) Received: from b01ledav003.gho.pok.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id B6D6DB2065; Tue, 2 Jul 2019 16:49:24 +0000 (GMT) Received: from paulmck-ThinkPad-W541 (unknown [9.70.82.26]) by b01ledav003.gho.pok.ibm.com (Postfix) with ESMTP; Tue, 2 Jul 2019 16:49:24 +0000 (GMT) Received: by paulmck-ThinkPad-W541 (Postfix, from userid 1000) id A133416C0FCF; Tue, 2 Jul 2019 09:49:24 -0700 (PDT) Date: Tue, 2 Jul 2019 09:49:24 -0700 From: "Paul E. McKenney" To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org Subject: Re: Signed-off-by for the fix-late-interrupts patch? Message-ID: <20190702164924.GX26519@linux.ibm.com> Reply-To: paulmck@linux.ibm.com References: <20190701213930.GA25736@linux.ibm.com> <20190702083632.GZ3419@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190702083632.GZ3419@hirez.programming.kicks-ass.net> User-Agent: Mutt/1.5.21 (2010-09-15) X-TM-AS-GCONF: 00 X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2019-07-02_08:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1907020183 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jul 02, 2019 at 10:36:32AM +0200, Peter Zijlstra wrote: > On Mon, Jul 01, 2019 at 02:39:31PM -0700, Paul E. McKenney wrote: > > Hello, Peter, > > > > The patch below from your earlier email is doing fine in my testing. > > May I please add your Signed-of-by and designate you as author? > > Sure, glad it worked :-) And here is the updated version, fixing a few typos along the way. If I don't hear otherwise from you, I will push it out via -rcu, but of course feel free to direct it elsewhere if you prefer. Thanx, Paul ------------------------------------------------------------------------ commit 559712d50c90fbaec1a6386d720deb323bb6468e Author: Peter Zijlstra Date: Wed Jun 5 07:46:43 2019 -0700 idle: Prevent late-arriving interrupts from disrupting offline Scheduling-clock interrupts can arrive late in the CPU-offline process, after idle entry and the subsequent call to cpuhp_report_idle_dead(). Once execution passes the call to rcu_report_dead(), RCU is ignoring the CPU, which results in lockdep complaints when the interrupt handler uses RCU: ------------------------------------------------------------------------ ============================= WARNING: suspicious RCU usage 5.2.0-rc1+ #681 Not tainted ----------------------------- kernel/sched/fair.c:9542 suspicious rcu_dereference_check() usage! other info that might help us debug this: RCU used illegally from offline CPU! rcu_scheduler_active = 2, debug_locks = 1 no locks held by swapper/5/0. stack backtrace: CPU: 5 PID: 0 Comm: swapper/5 Not tainted 5.2.0-rc1+ #681 Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS Bochs 01/01/2011 Call Trace: dump_stack+0x5e/0x8b trigger_load_balance+0xa8/0x390 ? tick_sched_do_timer+0x60/0x60 update_process_times+0x3b/0x50 tick_sched_handle+0x2f/0x40 tick_sched_timer+0x32/0x70 __hrtimer_run_queues+0xd3/0x3b0 hrtimer_interrupt+0x11d/0x270 ? sched_clock_local+0xc/0x74 smp_apic_timer_interrupt+0x79/0x200 apic_timer_interrupt+0xf/0x20 RIP: 0010:delay_tsc+0x22/0x50 Code: ff 0f 1f 80 00 00 00 00 65 44 8b 05 18 a7 11 48 0f ae e8 0f 31 48 89 d6 48 c1 e6 20 48 09 c6 eb 0e f3 90 65 8b 05 fe a6 11 48 <41> 39 c0 75 18 0f ae e8 0f 31 48 c1 e2 20 48 09 c2 48 89 d0 48 29 RSP: 0000:ffff8f92c0157ed0 EFLAGS: 00000212 ORIG_RAX: ffffffffffffff13 RAX: 0000000000000005 RBX: ffff8c861f356400 RCX: ffff8f92c0157e64 RDX: 000000321214c8cc RSI: 00000032120daa7f RDI: 0000000000260f15 RBP: 0000000000000005 R08: 0000000000000005 R09: 0000000000000000 R10: 0000000000000001 R11: 0000000000000001 R12: 0000000000000000 R13: 0000000000000000 R14: ffff8c861ee18000 R15: ffff8c861ee18000 cpuhp_report_idle_dead+0x31/0x60 do_idle+0x1d5/0x200 ? _raw_spin_unlock_irqrestore+0x2d/0x40 cpu_startup_entry+0x14/0x20 start_secondary+0x151/0x170 secondary_startup_64+0xa4/0xb0 ------------------------------------------------------------------------ This happens rarely, but can be forced by happen more often by placing delays in cpuhp_report_idle_dead() following the call to rcu_report_dead(). With this in place, the following rcutorture scenario reproduces the problem within a few minutes: tools/testing/selftests/rcutorture/bin/kvm.sh --cpus 8 --duration 5 --kconfig "CONFIG_DEBUG_LOCK_ALLOC=y CONFIG_PROVE_LOCKING=y" --configs "TREE04" This commit uses the crude but effective expedient of moving the disabling of interrupts within the idle loop to precede the cpu_is_offline() check. It also invokes tick_nohz_idle_stop_tick() instead of tick_nohz_idle_stop_tick_protected() to shut off the scheduling-clock interrupt, and then removes the latter because there are no other callers. Signed-off-by: Peter Zijlstra Cc: Frederic Weisbecker Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Paul E. McKenney diff --git a/include/linux/tick.h b/include/linux/tick.h index f92a10b5e112..196a0a7bfc4f 100644 --- a/include/linux/tick.h +++ b/include/linux/tick.h @@ -134,14 +134,6 @@ extern unsigned long tick_nohz_get_idle_calls(void); extern unsigned long tick_nohz_get_idle_calls_cpu(int cpu); extern u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time); extern u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time); - -static inline void tick_nohz_idle_stop_tick_protected(void) -{ - local_irq_disable(); - tick_nohz_idle_stop_tick(); - local_irq_enable(); -} - #else /* !CONFIG_NO_HZ_COMMON */ #define tick_nohz_enabled (0) static inline int tick_nohz_tick_stopped(void) { return 0; } @@ -164,8 +156,6 @@ static inline ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next) } static inline u64 get_cpu_idle_time_us(int cpu, u64 *unused) { return -1; } static inline u64 get_cpu_iowait_time_us(int cpu, u64 *unused) { return -1; } - -static inline void tick_nohz_idle_stop_tick_protected(void) { } #endif /* !CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL diff --git a/kernel/sched/idle.c b/kernel/sched/idle.c index f5516bae0c1b..42270ca90d94 100644 --- a/kernel/sched/idle.c +++ b/kernel/sched/idle.c @@ -240,13 +240,14 @@ static void do_idle(void) check_pgt_cache(); rmb(); + local_irq_disable(); + if (cpu_is_offline(cpu)) { - tick_nohz_idle_stop_tick_protected(); + tick_nohz_idle_stop_tick(); cpuhp_report_idle_dead(); arch_cpu_idle_dead(); } - local_irq_disable(); arch_cpu_idle_enter(); /*