linux-kernel - Suspicious rcu_dereference_check() usage detected during 2.6.34-rc6 boot on PPC64/p5 processor

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Date:	Thu, 06 May 2010 12:47:59 +0530
From:	Subrata Modak <subrata@...ux.vnet.ibm.com>
To:	Linuxppc-dev <Linuxppc-dev@...abs.org>,
	Paul Mackerras <paulus@....ibm.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	sachinp <sachinp@...ux.vnet.ibm.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	bnpoorni <bnpoorni@...ibm.com>
Subject: Suspicious rcu_dereference_check() usage detected during
	2.6.34-rc6 boot on PPC64/p5 processor

Hi,

The following messages were logged into /var/log/messages when i booted
2.6.34-rc6 kernel (built with attached CONFIG file contents ) on my p5 box:

...
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys debug
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys ns
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys cpuacct
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys memory
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys devices
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys freezer
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys net_cls
May  5 21:59:21 p550lp1 kernel: Initializing cgroup subsys blkio
May  5 21:59:21 p550lp1 kernel: ftrace: allocating 20193 entries in 119 pages
May  5 21:59:21 p550lp1 kernel:
May  5 21:59:21 p550lp1 kernel:
===================================================
May  5 21:59:21 p550lp1 kernel: [ INFO: suspicious rcu_dereference_check()
usage. ]
May  5 21:59:21 p550lp1 kernel:
---------------------------------------------------
May  5 21:59:21 p550lp1 kernel: include/linux/cgroup.h:533 invoked
rcu_dereference_check() without protection!
May  5 21:59:21 p550lp1 kernel:
May  5 21:59:21 p550lp1 kernel: other info that might help us debug this:
May  5 21:59:21 p550lp1 kernel:
May  5 21:59:21 p550lp1 kernel:
May  5 21:59:21 p550lp1 kernel: rcu_scheduler_active = 1, debug_locks = 0
May  5 21:59:21 p550lp1 kernel: no locks held by swapper/0.
May  5 21:59:21 p550lp1 kernel:
May  5 21:59:21 p550lp1 kernel: stack backtrace:
May  5 21:59:21 p550lp1 kernel: Call Trace:
May  5 21:59:21 p550lp1 kernel: [c00000000142f380] [c0000000000156b8]
.show_stack+0xb0/0x1a0 (unreliable)
May  5 21:59:21 p550lp1 kernel: [c00000000142f440] [c0000000007afd6c]
.dump_stack+0x28/0x3c
May  5 21:59:21 p550lp1 kernel: [c00000000142f4c0] [c0000000001081f0]
.lockdep_rcu_dereference+0xbc/0xe4
May  5 21:59:21 p550lp1 kernel: [c00000000142f560] [c0000000000b8d10]
.set_task_cpu+0x1b0/0x338
May  5 21:59:21 p550lp1 kernel: [c00000000142f770] [c0000000000b9860]
.sched_fork+0x104/0x164
May  5 21:59:21 p550lp1 kernel: [c00000000142f800] [c0000000000c0b88]
.copy_process+0x628/0x10a8
May  5 21:59:21 p550lp1 kernel: [c00000000142f900] [c0000000000c17a0]
.do_fork+0x198/0x438
May  5 21:59:21 p550lp1 kernel: [c00000000142fa40] [c000000000015bcc]
.sys_clone+0x88/0xb0
May  5 21:59:21 p550lp1 kernel: [c00000000142faf0] [c00000000000902c]
.ppc_clone+0x8/0xc
May  5 21:59:21 p550lp1 kernel: --- Exception: c00 at .kernel_thread+0x28/0x70
May  5 21:59:21 p550lp1 kernel:    LR = .rest_init+0x44/0x10c
May  5 21:59:21 p550lp1 kernel: [c00000000142fde0] [0000000001b5f988] 0x1b5f988
(unreliable)
May  5 21:59:21 p550lp1 kernel: [c00000000142fe50] [c00000000000a664]
.rest_init+0x30/0x10c
May  5 21:59:21 p550lp1 kernel: [c00000000142fee0] [c000000000ab8e38]
.start_kernel+0x4ec/0x510
May  5 21:59:21 p550lp1 kernel: [c00000000142ff90] [c000000000008c64]
.start_here_common+0x2c/0x48
May  5 21:59:21 p550lp1 kernel: Processor 1 found.
May  5 21:59:21 p550lp1 kernel: Processor 2 found.
...

Regards--
Subrata


View attachment "config-2.6.34-rc6" of type "text/plain" (101520 bytes)