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Mon, 19 Jul 2021 00:32:19 -0700 (PDT) Received: from [192.168.1.10] ([94.10.31.26]) by smtp.googlemail.com with ESMTPSA id m32sm18455949wms.23.2021.07.19.00.32.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 19 Jul 2021 00:32:18 -0700 (PDT) Subject: Re: linux-5.13.2: warning from kernel/rcu/tree_plugin.h:359 To: paulmck@kernel.org, Oleksandr Natalenko Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org, Chris Rankin , Josh Triplett , Steven Rostedt , Mathieu Desnoyers , Lai Jiangshan , Joel Fernandes , rcu@vger.kernel.org, Andrew Morton , linux-mm@kvack.org References: <2245518.LNIG0phfVR@natalenko.name> <6698965.kvI7vG0SvZ@natalenko.name> <20210718215914.GQ4397@paulmck-ThinkPad-P17-Gen-1> From: Chris Clayton Message-ID: Date: Mon, 19 Jul 2021 08:32:16 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0 MIME-Version: 1.0 In-Reply-To: <20210718215914.GQ4397@paulmck-ThinkPad-P17-Gen-1> Content-Type: text/plain; charset=utf-8 Content-Language: en-GB X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: C7B7750000A0 X-Stat-Signature: bd9tno514t1xon6nawb7858wgottg5b5 Authentication-Results: imf04.hostedemail.com; dkim=pass header.d=googlemail.com header.s=20161025 header.b=YMH7ZePX; spf=pass (imf04.hostedemail.com: domain of chris2553@googlemail.com designates 209.85.221.53 as permitted sender) smtp.mailfrom=chris2553@googlemail.com; dmarc=pass (policy=quarantine) header.from=googlemail.com X-HE-Tag: 1626679940-101756 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 18/07/2021 22:59, Paul E. McKenney wrote: > On Sun, Jul 18, 2021 at 11:03:51PM +0200, Oleksandr Natalenko wrote: >> + stable@vger.kernel.org >> >> On ned=C4=9Ble 18. =C4=8Dervence 2021 23:01:24 CEST Oleksandr Natalenk= o wrote: >>> Hello. >>> >>> On sobota 17. =C4=8Dervence 2021 22:22:08 CEST Chris Clayton wrote: >>>> I checked the output from dmesg yesterday and found the following wa= rning: >>>> >>>> [Fri Jul 16 09:15:29 2021] ------------[ cut here ]------------ >>>> [Fri Jul 16 09:15:29 2021] WARNING: CPU: 11 PID: 2701 at >>>> kernel/rcu/tree_plugin.h:359 rcu_note_context_switch+0x37/0x3d0 [Fri= Jul >>>> 16 >=20 > I am not seeing a warning at line 359 of either v5.13.2 or v5.12.7. >=20 Mmm, in the 5.13.2 tarball downloaded from https://cdn.kernel.org/pub/lin= ux/kernel/v5.x/ I see: 350 */ 351 void rcu_note_context_switch(bool preempt) 352 { 353 struct task_struct *t =3D current; 354 struct rcu_data *rdp =3D this_cpu_ptr(&rcu_data); 355 struct rcu_node *rnp; 356 357 trace_rcu_utilization(TPS("Start context switch")); 358 lockdep_assert_irqs_disabled(); 359 WARN_ON_ONCE(!preempt && rcu_preempt_depth() > 0); 360 if (rcu_preempt_depth() > 0 && 361 !t->rcu_read_unlock_special.b.blocked) { 362 >>>> 09:15:29 2021] Modules linked in: uas hidp rfcomm bnep xt_MASQUERADE >>>> iptable_nat nf_nat xt_LOG nf_log_syslog xt_limit xt_multiport xt_con= ntrack >>>> iptable_filter btusb btintel wmi_bmof uvcvideo videobuf2_vmalloc >>>> videobuf2_memops videobuf2_v4l2 videobuf2_common coretemp hwmon >>>> snd_hda_codec_hdmi x86_pkg_temp_thermal snd_hda_codec_realtek >>>> snd_hda_codec_generic ledtrig_audio snd_hda_intel snd_intel_dspcfg >>>> snd_hda_codec snd_hwdep snd_hda_core i2c_i801 i2c_smbus iwlmvm mac80= 211 >>>> iwlwifi i915 mei_me mei cfg80211 intel_lpss_pci intel_lpss wmi >>>> nf_conntrack_ftp xt_helper nf_conntrack nf_defrag_ipv4 tun >>>> [Fri Jul 16 09:15:29 2021] CPU: 11 PID: 2701 Comm: lpqd Not tainted = 5.13.2 >>>> #1 [Fri Jul 16 09:15:29 2021] Hardware name: Notebook >>>> >>>> NP50DE_DB /NP50DE_DB , BIOS 1.07.04 02/17/20= 20 >>>> >>>> [Fri Jul 16 09:15:29 2021] RIP: 0010:rcu_note_context_switch+0x37/0x= 3d0 >>>> [Fri Jul 16 09:15:29 2021] Code: 02 00 e8 ec a0 6c 00 89 c0 65 4c 8b= 2c 25 >>>> 00 6d 01 00 48 03 1c c5 80 56 e1 b6 40 84 ed 75 0d 41 8b 95 04 03 00= 00 85 >>>> d2 7e 02 <0f> 0b 65 48 8b 04 25 00 6d 01 00 8b 80 04 03 00 00 85 c0 = 7e 0a >>>> 41 [Fri Jul 16 09:15:29 2021] RSP: 0000:ffffb5d483837c70 EFLAGS: 000= 10002 >>>> [Fri Jul 16 09:15:29 2021] RAX: 000000000000000b RBX: ffff9b77806e1d= 80 >>>> RCX: >>>> 0000000000000100 [Fri Jul 16 09:15:29 2021] RDX: 0000000000000001 RS= I: >>>> ffffffffb6d82ead RDI: ffffffffb6da5e4e [Fri Jul 16 09:15:29 2021] RB= P: >>>> 0000000000000000 R08: 0000000000000001 R09: 0000000000000000 [Fri Ju= l 16 >>>> 09:15:29 2021] R10: 000000067bce4fff R11: 0000000000000000 R12: >>>> ffff9b77806e1100 [Fri Jul 16 09:15:29 2021] R13: ffff9b734a833a00 R1= 4: >>>> ffff9b734a833a00 R15: 0000000000000000 [Fri Jul 16 09:15:29 2021] FS= : >>>> 00007fccbfc5fe40(0000) GS:ffff9b77806c0000(0000) knlGS:0000000000000= 000 >>>> [Fri Jul 16 09:15:29 2021] CS: 0010 DS: 0000 ES: 0000 CR0: >>>> 0000000080050033 [Fri Jul 16 09:15:29 2021] CR2: 00007fccc2db7290 CR= 3: >>>> 00000003fb0b8002 CR4: 00000000007706e0 [Fri Jul 16 09:15:29 2021] PK= RU: >>>> 55555554 >>>> [Fri Jul 16 09:15:29 2021] Call Trace: >>>> [Fri Jul 16 09:15:29 2021] __schedule+0x86/0x810 >>>> [Fri Jul 16 09:15:29 2021] schedule+0x40/0xe0 >>>> [Fri Jul 16 09:15:29 2021] io_schedule+0x3d/0x60 >>>> [Fri Jul 16 09:15:29 2021] wait_on_page_bit_common+0x129/0x390 >>>> [Fri Jul 16 09:15:29 2021] ? __filemap_set_wb_err+0x10/0x10 >>>> [Fri Jul 16 09:15:29 2021] __lock_page_or_retry+0x13f/0x1d0 >>>> [Fri Jul 16 09:15:29 2021] do_swap_page+0x335/0x5b0 >>>> [Fri Jul 16 09:15:29 2021] __handle_mm_fault+0x444/0xb20 >>>> [Fri Jul 16 09:15:29 2021] handle_mm_fault+0x5c/0x170 >>>> [Fri Jul 16 09:15:29 2021] ? find_vma+0x5b/0x70 >>>> [Fri Jul 16 09:15:29 2021] exc_page_fault+0x1ab/0x610 >>>> [Fri Jul 16 09:15:29 2021] ? fpregs_assert_state_consistent+0x19/0x= 40 >>>> [Fri Jul 16 09:15:29 2021] ? asm_exc_page_fault+0x8/0x30 >>>> [Fri Jul 16 09:15:29 2021] asm_exc_page_fault+0x1e/0x30 >>>> [Fri Jul 16 09:15:29 2021] RIP: 0033:0x7fccc2d3c520 >>>> [Fri Jul 16 09:15:29 2021] Code: 68 4c 00 00 00 e9 20 fb ff ff ff 25= 7a ad >>>> 07 00 68 4d 00 00 00 e9 10 fb ff ff ff 25 72 ad 07 00 68 4e 00 00 00= e9 00 >>>> fb ff ff 25 6a ad 07 00 68 4f 00 00 00 e9 f0 fa ff ff ff 25 62 = ad 07 >>>> 00 [Fri Jul 16 09:15:29 2021] RSP: 002b:00007ffebd529048 EFLAGS: 000= 10293 >>>> [Fri Jul 16 09:15:29 2021] RAX: 0000000000000001 RBX: 00007fccc46e28= 90 >>>> RCX: >>>> 0000000000000010 [Fri Jul 16 09:15:29 2021] RDX: 0000000000000010 RS= I: >>>> 0000000000000000 RDI: 00007fccc46e2890 [Fri Jul 16 09:15:29 2021] RB= P: >>>> 000056264f1dd4a0 R08: 000056264f21aba0 R09: 000056264f1f58a0 [Fri Ju= l 16 >>>> 09:15:29 2021] R10: 0000000000000007 R11: 0000000000000246 R12: >>>> 000056264f21ac00 [Fri Jul 16 09:15:29 2021] R13: 000056264f1e0a30 R1= 4: >>>> 00007ffebd529080 R15: 00000000000dd87b [Fri Jul 16 09:15:29 2021] --= -[ end >>>> trace c8b06e067d8b0fc2 ]--- >>>> >>>> At the time the warning was issued I was creating a (weekly) backup = of my >>>> linux system (home-brewed based on the guidance from Linux From Scra= tch). >>>> My backup routine is completed by copying the archive files (created= with >>>> dar) and a directory that contains about 7000 source and binary rpm = files >>>> to an external USB drive. I didn't spot the warning until later in t= he >>>> day, >>>> so I'm not sure exactly where I was in my backup process. >>>> >>>> I haven't seen this warning before. Consequently, I don;t know how e= asy >>>> (or >>>> otherwise) it is to reproduce. >>>> >>>> Let me know if I can provide any additional diagnostics, but please = cc me >>>> as I'm not subscribed. >>> >>> Confirming the same for me with v5.13.2, and cross-referencing anothe= r >>> report [1] against v5.12.17. >>> >>> Also Cc'ing relevant people on this. >>> >>> Thanks. >>> >>> [1] >>> https://lore.kernel.org/lkml/CAK2bqVK0Q9YcpakE7_Rc6nr-E4e2GnMOgi5jJj=3D= _Eh_1k >>> EHLHA@mail.gmail.com/ >=20 > But this one does show this warning in v5.12.17: >=20 > WARN_ON_ONCE(!preempt && rcu_preempt_depth() > 0); >=20 > This is in rcu_note_context_switch(), and could be caused by something > like a schedule() within an RCU read-side critical section. This would > of course be RCU-usage bugs, given that you are not permitted to block > within an RCU read-side critical section. >=20 > I suggest checking the functions in the stack trace to see where the > rcu_read_lock() is hiding. CONFIG_PROVE_LOCKING might also be helpful. >=20 > Thanx, Paul >=20