From patchwork Wed Sep 14 02:15:28 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Zhouyi Zhou X-Patchwork-Id: 12975485 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3C825ECAAD8 for ; Wed, 14 Sep 2022 02:15:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229638AbiINCPp (ORCPT ); Tue, 13 Sep 2022 22:15:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45518 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229812AbiINCPn (ORCPT ); Tue, 13 Sep 2022 22:15:43 -0400 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF6ED47BB2; Tue, 13 Sep 2022 19:15:42 -0700 (PDT) Received: by mail-pj1-x1034.google.com with SMTP id fv3so13121754pjb.0; Tue, 13 Sep 2022 19:15:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date; bh=HLs00qLGkRYsRs/Qs4OSx3zhLgfT7QPCYF2RVcp6Dnw=; b=JVNZrBvMEakmiimzfvMyEqUuOFoaYIxkE7IZ6Uiqx8ikeXCbZRH5jC37NcZLjJKTvh QPw7wQu7uaKL3PlIrh+anQoiFPZwItj9hdbbsD/0zpJ/GKCym2WnVOK3SqoPeUmR5Z/H ctDUd4rdvbo8HEsFWVxJHnfJSnEtJFPT2B7TgDk68tpHAeQKz9lEJWi18WHGY4/Lh8Yg Q7r6TU51e6DsklGPC1DsFRX2WbkE4gPYE0hL8Gji/2tkRxFlNRksj/oS7J9iiuaUyAXV kJ8YRqQ3RNpIKPPIj/e04lKMOPkz1xARs4Rzzyihjqf46cXXbm1pUkJXvPVZS6XHYFln 4a5w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date; bh=HLs00qLGkRYsRs/Qs4OSx3zhLgfT7QPCYF2RVcp6Dnw=; b=vNuChH6tVnzKPeydUTmjhiMzBff43aL0E2WKkCEaCbCT+QHmsDLKKoKA8IBVCkkYYa r/KXHNJHXP50fcFEW2XoWqm4LtTuPjClwsEHaRF2fkvrqMq8CO7sIawN079PQBG9PxK2 12HGCLuj1F9qjDclPQyK3YUJD3KTt3WsroA2uphasfvznsAof1X2GOLFX3QNAPzslGcJ mFAHyyEtab/PEg3EDo5ism4Me9tPIwKAVezZlfFfDVaieI43+KYxm2qBoJL6MSR0pCA4 hdEfXgQje/HbVs/OgchRImu4gdGAE1HbRTiFXDShrUemjUi4ET1oU+BXWKQdLZstvJts fFzQ== X-Gm-Message-State: ACrzQf0g3rswleO4hSdETAwhF7bY0dF5lleu0fA3p+xJkS7Wm1yeoIIg wxDQU/3Zf6pjIr0HoVlQTB4= X-Google-Smtp-Source: AMsMyM7R+4iL3pfpcVaoK8BnJh2Kbp150IOZXSMqzOihpjKT1NL6dCeS4RSsgTkeIzZhBLJm1DuOzA== X-Received: by 2002:a17:90b:3909:b0:202:c879:51a9 with SMTP id ob9-20020a17090b390900b00202c87951a9mr2168744pjb.83.1663121742226; Tue, 13 Sep 2022 19:15:42 -0700 (PDT) Received: from localhost.localdomain ([194.5.48.32]) by smtp.gmail.com with ESMTPSA id f13-20020a170902684d00b0016ed8af2ec0sm9343655pln.29.2022.09.13.19.15.38 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 13 Sep 2022 19:15:41 -0700 (PDT) From: Zhouyi Zhou To: mpe@ellerman.id.au, npiggin@gmail.com, christophe.leroy@csgroup.eu, atrajeev@linux.vnet.ibm.com, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, lance@osuosl.org, paulmck@kernel.org, rcu@vger.kernel.org Cc: Zhouyi Zhou Subject: [PATCH linux-next][RFC] powerpc: protect cpu offlining by RCU offline lock Date: Wed, 14 Sep 2022 10:15:28 +0800 Message-Id: <20220914021528.15946-1-zhouzhouyi@gmail.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: rcu@vger.kernel.org During the cpu offlining, the sub functions of xive_teardown_cpu will call __lock_acquire when CONFIG_LOCKDEP=y. The latter function will travel RCU protected list, so "WARNING: suspicious RCU usage" will be triggered. Try to protect cpu offlining by RCU offline lock. Tested on PPC VM of Open Source Lab of Oregon State University. (Each round of tests takes about 19 hours to finish) Test results show that although "WARNING: suspicious RCU usage" has gone, but there are more "BUG: soft lockup" reports than the original kernel (10 vs 6), so I add a [RFC] to my subject line. Signed-off-by: Zhouyi Zhou --- [it seems that there are some delivery problem in my previous email, so I send again via gmail, sorry for the trouble] Dear PPC and RCU developers I found this bug when trying to do rcutorture tests in ppc VM of Open Source Lab of Oregon State University. console.log report following bug: [ 37.635545][ T0] WARNING: suspicious RCU usage^M [ 37.636409][ T0] 6.0.0-rc4-next-20220907-dirty #8 Not tainted^M [ 37.637575][ T0] -----------------------------^M [ 37.638306][ T0] kernel/locking/lockdep.c:3723 RCU-list traversed in non-reader section!!^M [ 37.639651][ T0] ^M [ 37.639651][ T0] other info that might help us debug this:^M [ 37.639651][ T0] ^M [ 37.641381][ T0] ^M [ 37.641381][ T0] RCU used illegally from offline CPU!^M [ 37.641381][ T0] rcu_scheduler_active = 2, debug_locks = 1^M [ 37.667170][ T0] no locks held by swapper/6/0.^M [ 37.668328][ T0] ^M [ 37.668328][ T0] stack backtrace:^M [ 37.669995][ T0] CPU: 6 PID: 0 Comm: swapper/6 Not tainted 6.0.0-rc4-next-20220907-dirty #8^M [ 37.672777][ T0] Call Trace:^M [ 37.673729][ T0] [c000000004653920] [c00000000097f9b4] dump_stack_lvl+0x98/0xe0 (unreliable)^M [ 37.678579][ T0] [c000000004653960] [c0000000001f2eb8] lockdep_rcu_suspicious+0x148/0x16c^M [ 37.680425][ T0] [c0000000046539f0] [c0000000001ed9b4] __lock_acquire+0x10f4/0x26e0^M [ 37.682450][ T0] [c000000004653b30] [c0000000001efc2c] lock_acquire+0x12c/0x420^M [ 37.684113][ T0] [c000000004653c20] [c0000000010d704c] _raw_spin_lock_irqsave+0x6c/0xc0^M [ 37.686154][ T0] [c000000004653c60] [c0000000000c7b4c] xive_spapr_put_ipi+0xcc/0x150^M [ 37.687879][ T0] [c000000004653ca0] [c0000000010c72a8] xive_cleanup_cpu_ipi+0xc8/0xf0^M [ 37.689856][ T0] [c000000004653cf0] [c0000000010c7370] xive_teardown_cpu+0xa0/0xf0^M [ 37.691877][ T0] [c000000004653d30] [c0000000000fba5c] pseries_cpu_offline_self+0x5c/0x100^M [ 37.693882][ T0] [c000000004653da0] [c00000000005d2c4] arch_cpu_idle_dead+0x44/0x60^M [ 37.695739][ T0] [c000000004653dc0] [c0000000001c740c] do_idle+0x16c/0x3d0^M [ 37.697536][ T0] [c000000004653e70] [c0000000001c7a1c] cpu_startup_entry+0x3c/0x40^M [ 37.699694][ T0] [c000000004653ea0] [c00000000005ca20] start_secondary+0x6c0/0xb50^M [ 37.701742][ T0] [c000000004653f90] [c00000000000d054] start_secondary_prolog+0x10/0x14^M I am a beginner, hope I can be of some beneficial to the community ;-) Thanks Zhouyi -- arch/powerpc/platforms/pseries/hotplug-cpu.c | 5 ++++- include/linux/rcupdate.h | 3 ++- kernel/rcu/tree.c | 10 ++++++++++ 3 files changed, 16 insertions(+), 2 deletions(-) diff --git a/arch/powerpc/platforms/pseries/hotplug-cpu.c b/arch/powerpc/platforms/pseries/hotplug-cpu.c index 0f8cd8b06432..ddf66a253c70 100644 --- a/arch/powerpc/platforms/pseries/hotplug-cpu.c +++ b/arch/powerpc/platforms/pseries/hotplug-cpu.c @@ -64,11 +64,14 @@ static void pseries_cpu_offline_self(void) local_irq_disable(); idle_task_exit(); + + /* Because the cpu is now offline, let rcu know that */ + rcu_state_ofl_lock(); if (xive_enabled()) xive_teardown_cpu(); else xics_teardown_cpu(); - + rcu_state_ofl_unlock(); unregister_slb_shadow(hwcpu); rtas_stop_self(); diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h index 63d2e6a60ad7..d857955a02ba 100644 --- a/include/linux/rcupdate.h +++ b/include/linux/rcupdate.h @@ -1034,5 +1034,6 @@ rcu_head_after_call_rcu(struct rcu_head *rhp, rcu_callback_t f) /* kernel/ksysfs.c definitions */ extern int rcu_expedited; extern int rcu_normal; - +void rcu_state_ofl_lock(void); +void rcu_state_ofl_unlock(void); #endif /* __LINUX_RCUPDATE_H */ diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 6bb8e72bc815..3282725f1054 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -4796,6 +4796,16 @@ void __init rcu_init(void) (void)start_poll_synchronize_rcu_expedited(); } +void rcu_state_ofl_lock(void) +{ + arch_spin_lock(&rcu_state.ofl_lock); +} + +void rcu_state_ofl_unlock(void) +{ + arch_spin_unlock(&rcu_state.ofl_lock); +} + #include "tree_stall.h" #include "tree_exp.h" #include "tree_nocb.h"