Re: 2.6.35-rc2-git1 - include/linux/cgroup.h:534 invoked rcu_dereference_check() without protection!

[Miles Lane]

On Wed, Jun 9, 2010 at 11:29 AM, Miles Lane <miles.lane@xxxxxxxxx> wrote:
> On Wed, Jun 9, 2010 at 11:24 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
>> On Wed, 2010-06-09 at 11:11 -0400, Miles Lane wrote:
>>>
>>> Sorry.  I misunderstood this message when I first read it.  I didn't
>>> realize this message include a new version of the patch.
>>> Anyhow, I just tried to apply the patch to 2.6.35-rc2-git3 and got this:
>>>
>>> # patch -p1 -l -F 20 --dry-run < ../5.patch
>>> patching file include/linux/cgroup.h
>>> patching file kernel/sched.c
>>> Hunk #1 succeeded at 306 with fuzz 1.
>>> Hunk #3 FAILED at 4462.
>>> Hunk #4 succeeded at 4487 with fuzz 3.
>>> 1 out of 4 hunks FAILED -- saving rejects to file kernel/sched.c.rej
>>
>> Weird.. it seems to apply without trouble to Linus' git tree.
>>
>> root@twins:/usr/src/linux-2.6# git checkout -f origin/master
>> HEAD is now at 84f7586... Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ieee1394/linux1394-2.6
>> root@twins:/usr/src/linux-2.6# quilt push
>> Applying patch patches/sched-rcu-validation.patch
>> patching file include/linux/cgroup.h
>> patching file kernel/sched.c
>>
>> Now at patch patches/sched-rcu-validation.patch
>> root@twins:/usr/src/linux-2.6# git describe
>> v2.6.35-rc2-54-g84f7586
>
> Oh.  Duh. I know what is going on.  I had received another patch to
> sched.c.  They must conflict.  I will test with just your patch now.
>

ACPI: Core revision 20100428
[    0.061088]
[    0.061090] ===================================================
[    0.062009] [ INFO: suspicious rcu_dereference_check() usage. ]
[    0.062138] ---------------------------------------------------
[    0.062268] kernel/sched.c:616 invoked rcu_dereference_check()
without protection!
[    0.062470]
[    0.062471] other info that might help us debug this:
[    0.062472]
[    0.062835]
[    0.062836] rcu_scheduler_active = 1, debug_locks = 1
[    0.063009] no locks held by swapper/0.
[    0.063134]
[    0.063135] stack backtrace:
[    0.063378] Pid: 0, comm: swapper Not tainted 2.6.35-rc2-git3 #3
[    0.063507] Call Trace:
[    0.063638]  [<ffffffff81072205>] lockdep_rcu_dereference+0x9d/0xa5
[    0.063773]  [<ffffffff810379f9>] task_group+0x7b/0x8a
[    0.064012]  [<ffffffff81037a1d>] set_task_rq+0x15/0x6e
[    0.064143]  [<ffffffff8103e50f>] set_task_cpu+0xa9/0xba
[    0.064274]  [<ffffffff81042dbb>] sched_fork+0x10a/0x1b3
[    0.064405]  [<ffffffff810446f9>] copy_process+0x617/0x10e6
[    0.064537]  [<ffffffff8104533d>] do_fork+0x175/0x39b
[    0.064670]  [<ffffffff8106589b>] ? up+0xf/0x39
[    0.064800]  [<ffffffff8106589b>] ? up+0xf/0x39
[    0.065013]  [<ffffffff811dbf73>] ? do_raw_spin_lock+0x79/0x13e
[    0.065148]  [<ffffffff81011526>] kernel_thread+0x70/0x72
[    0.065279]  [<ffffffff816cc5e4>] ? kernel_init+0x0/0x1ce
[    0.065411]  [<ffffffff8100aba0>] ? kernel_thread_helper+0x0/0x10
[    0.065545]  [<ffffffff81096bea>] ? rcu_scheduler_starting+0x2a/0x4c
[    0.065679]  [<ffffffff813a8a4d>] rest_init+0x21/0xde
[    0.065810]  [<ffffffff816cce28>] start_kernel+0x448/0x453
[    0.066013]  [<ffffffff816cc2c8>] x86_64_start_reservations+0xb3/0xb7
[    0.066148]  [<ffffffff816cc418>] x86_64_start_kernel+0x14c/0x15b
[    0.066499] Setting APIC routing to flat
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