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SubjectRe: INFO: suspicious rcu_dereference_check() usage - include/linux/cgroup.h:492 invoked rcu_dereference_check() without protection!
From
On Wed, Mar 10, 2010 at 11:28 PM, Paul E. McKenney
<paulmck@linux.vnet.ibm.com> wrote:
> On Sun, Mar 07, 2010 at 08:26:53PM -0500, Miles Lane wrote:
>> [    0.000000] Memory: 4004344k/5242880k available (5147k kernel code,
>> 1084452k absent, 154084k reserved, 5943k data, 520k init)
>> [    0.000000] SLUB: Genslabs=13, HWalign=64, Order=0-3, MinObjects=0,
>> CPUs=2, Nodes=1
>> [    0.000000]
>> [    0.000000] ===================================================
>> [    0.000000] [ INFO: suspicious rcu_dereference_check() usage. ]
>> [    0.000000] ---------------------------------------------------
>> [    0.000000] include/linux/cgroup.h:492 invoked
>> rcu_dereference_check() without protection!
>
> Hello, Miles,
>
> This one is a false positive that is addressed by a set of boot-time
> fixes that have recently gone into mainline, this series of commits:
>
>        c598a070..71da8132
>
>                                                        Thanx, Paul

I know you indicated this was fixed in mainline and I see that set of
commits objects, but I'm seeing the below spew from linux-next today.

tree: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
tag: next-20100412
commit: bbeecf185fe464ccd7ee97ce6d3646ad686995b4

[ 0.035602] ===================================================
[ 0.036003] [ INFO: suspicious rcu_dereference_check() usage. ]
[ 0.037006] ---------------------------------------------------
[ 0.038004] include/linux/cgroup.h:533 invoked
rcu_dereference_check() without protection!
[ 0.039003]
[ 0.039004] other info that might help us debug this:
[ 0.039004]
[ 0.040003]
[ 0.040004] rcu_scheduler_active = 1, debug_locks = 0
[ 0.041004] no locks held by swapper/0.
[ 0.042003]
[ 0.042004] stack backtrace:
[ 0.043005] Pid: 0, comm: swapper Not tainted 2.6.34-rc3-next-20100412+ #65
[ 0.044003] Call Trace:
[ 0.045015] [<ffffffff8108584f>] lockdep_rcu_dereference+0xaf/0xc0
[ 0.046010] [<ffffffff81044812>] set_task_cpu+0x2d2/0x370
[ 0.047009] [<ffffffff814dfef5>] ? _raw_spin_unlock_irqrestore+0x65/0x80
[ 0.048006] [<ffffffff81087aa0>] ? trace_hardirqs_on_caller+0x120/0x1a0
[ 0.049006] [<ffffffff81087b2d>] ? trace_hardirqs_on+0xd/0x10
[ 0.050006] [<ffffffff814dfed9>] ? _raw_spin_unlock_irqrestore+0x49/0x80
[ 0.051005] [<ffffffff8104a7a6>] ? task_fork_fair+0xc6/0x390
[ 0.052005] [<ffffffff810497b4>] sched_fork+0x74/0x170
[ 0.053006] [<ffffffff81054a3f>] copy_process+0x62f/0x11e0
[ 0.054006] [<ffffffff810882bd>] ? validate_chain+0x4fd/0x1360
[ 0.055005] [<ffffffff810556ae>] do_fork+0xbe/0x3e0
[ 0.056008] [<ffffffff81012519>] ? sched_clock+0x9/0x10
[ 0.057008] [<ffffffff81077485>] ? sched_clock_local+0x15/0x80
[ 0.058005] [<ffffffff810775ab>] ? sched_clock_cpu+0xbb/0xf0
[ 0.059005] [<ffffffff81076415>] ? up+0x35/0x50
[ 0.060005] [<ffffffff81083623>] ? get_lock_stats+0x23/0x70
[ 0.061005] [<ffffffff8108367e>] ? put_lock_stats+0xe/0x30
[ 0.062011] [<ffffffff81aa6e20>] ? kernel_init+0x0/0x2e0
[ 0.063007] [<ffffffff810136dd>] kernel_thread+0x8d/0xa0
[ 0.064007] [<ffffffff81aa6e20>] ? kernel_init+0x0/0x2e0
[ 0.065009] [<ffffffff8100bc20>] ? kernel_thread_helper+0x0/0x10
[ 0.066006] [<ffffffff81aa6140>] ? early_idt_handler+0x0/0x71
[ 0.067006] [<ffffffff814c5cf1>] rest_init+0x21/0x110
[ 0.068006] [<ffffffff81aa6d3f>] start_kernel+0x3af/0x490
[ 0.069006] [<ffffffff81aa629c>] x86_64_start_reservations+0x7c/0xd0
[ 0.070006] [<ffffffff81aa6000>] ? early_idt_handlers+0x0/0x140
[ 0.071006] [<ffffffff81aa63e8>] x86_64_start_kernel+0xf8/0x130
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