linux-kernel - [lkp] [tracing] 633f6f58af: INFO: suspicious RCU usage

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Message-ID: <20160311070723.GA32315@yexl-desktop>
Date:	Fri, 11 Mar 2016 15:07:23 +0800
From:	kernel test robot <xiaolong.ye@...el.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	"Shreyas B. Prabhu" <shreyas@...ux.vnet.ibm.com>,
	LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: [lkp] [tracing] 633f6f58af: INFO: suspicious RCU usage

FYI, we noticed the dmesgs warning on

https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
commit 633f6f58af445022e38417599a4789b5fc510b71 ("tracing: Remove duplicate checks for online CPUs")


+-------------------------------------+------------+------------+
|                                     | d39cdd2036 | 633f6f58af |
+-------------------------------------+------------+------------+
| INFO:suspicious_RCU_usage           | 0          | 11         |
| RCU_used_illegally_from_offline_CPU | 0          | 11         |
| backtrace:cpu_startup_entry         | 0          | 11         |
+-------------------------------------+------------+------------+



[    7.181678] numa_remove_cpu cpu 0 node 0: mask now 1
[    7.183715] 
[    7.183948] ===============================
[    7.184546] [ INFO: suspicious RCU usage. ]
[    7.185140] 4.5.0-rc7-00002-g633f6f5 #1 Not tainted
[    7.185831] -------------------------------
[    7.186425] include/trace/events/tlb.h:56 suspicious rcu_dereference_check() usage!
[    7.187755] 
[    7.187755] other info that might help us debug this:
[    7.187755] 
[    7.188874] 
[    7.188874] RCU used illegally from offline CPU!
[    7.188874] rcu_scheduler_active = 1, debug_locks = 0
[    7.190426] no locks held by swapper/0/0.
[    7.190995] 
[    7.190995] stack backtrace:
[    7.191614] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.5.0-rc7-00002-g633f6f5 #1
[    7.192659] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Debian-1.8.2-1 04/01/2014
[    7.193891]  0000000000000000 ffffffff81e03e20 ffffffff8139477c ffffffff81e0f500
[    7.195004]  0000000000000001 ffffffff81e03e50 ffffffff810e29cb ffff8800107a0b00
[    7.196116]  ffffffff81e76a40 0000000000000000 ffff8800107a0e98 ffffffff81e03e68
[    7.197229] Call Trace:
[    7.197592]  [<ffffffff8139477c>] dump_stack+0x81/0xb6
[    7.198313]  [<ffffffff810e29cb>] lockdep_rcu_suspicious+0xf7/0x100
[    7.199193]  [<ffffffff810c64b5>] trace_tlb_flush+0x96/0xf1
[    7.200130]  [<ffffffff810c65d0>] switch_mm+0x73/0x11d
[    7.200957]  [<ffffffff810cb92e>] idle_task_exit+0x67/0x74
[    7.201731]  [<ffffffff81036888>] play_dead_common+0xe/0x42
[    7.202516]  [<ffffffff810368cd>] native_play_dead+0x11/0x104
[    7.203318]  [<ffffffff8100f0db>] arch_cpu_idle_dead+0xf/0x11
[    7.204127]  [<ffffffff810dbd27>] cpu_startup_entry+0xdd/0x30a
[    7.204951]  [<ffffffff816d3d93>] rest_init+0x13a/0x140
[    7.205694]  [<ffffffff821a6f91>] start_kernel+0x4b1/0x4be
[    7.206470]  [<ffffffff821a6120>] ? early_idt_handler_array+0x120/0x120
[    7.207395]  [<ffffffff821a6315>] x86_64_start_reservations+0x2a/0x2c
[    7.208297]  [<ffffffff821a6444>] x86_64_start_kernel+0x12d/0x13a
[    7.238450] CPU 0 is now offline
[    7.240139] debug: unmapping init [mem 0xffffffff81fcf000-0xffffffff82297fff]
[    7.242450] Write protecting the kernel read-only data: 14336k




Thanks,
Xiaolong Ye

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