Prev: [RFC] Save/restore MISC_ENABLE register
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From: Miles Lane on 9 Jun 2010 13:10
On Wed, Jun 9, 2010 at 11:29 AM, Miles Lane <miles.lane(a)gmail.com> wrote:
> On Wed, Jun 9, 2010 at 11:24 AM, Peter Zijlstra <peterz(a)infradead.org> 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(a)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(a)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(a)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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From: Miles Lane on 9 Jun 2010 17:20
On Wed, Jun 9, 2010 at 2:15 PM, Peter Zijlstra <peterz(a)infradead.org> wrote:
> On Wed, 2010-06-09 at 19:57 +0200, Peter Zijlstra wrote:
>> + � � � /*
>> + � � � �* We're not in the pid-hash yet so no cgroup attach races, and the
>> + � � � �* cgroup is pinned by the parent running this.
>> + � � � �*
>> + � � � �* Silence PROVE_RCU.
>> + � � � �*/
>
> Hum,.. not sure that's actually true though, the parent itself is still
> susceptible to races afaict..

Do you want what you sent earlier tested, or should I wait for another patch?
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Prev: [RFC] Save/restore MISC_ENABLE register
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