Re: [tip:core/rcu] Revert "rcu: Decrease memory-barrier usage basedon semi-formal proof"

From: Yinghai Lu
Date: Mon May 23 2011 - 16:15:00 EST

On 05/21/2011 07:08 AM, Paul E. McKenney wrote:
> On Sat, May 21, 2011 at 06:18:44AM -0700, Paul E. McKenney wrote:
>> On Fri, May 20, 2011 at 05:02:40PM -0700, Yinghai Lu wrote:
>>> On 05/20/2011 04:49 PM, Paul E. McKenney wrote:
>>>> On Fri, May 20, 2011 at 04:16:28PM -0700, Yinghai Lu wrote:
>>> ...
>>>>>
>>>>> the same one i sent out before, but let DEBUG_LOCKING_API_SELFTESTS disabled.
>>>>
>>>> OK, just to make sure I understand... You are compiling exactly the
>>>> same kernel source tree with exactly the same .config, just with two
>>>> different versions of gcc, correct?
>>> yes.
>>>>
>>>> If so, it is quite possible that the slow one is the correct one. :-/
>>> yeah, new version always have problem.
>>>
>>> looks like opensuse11.3 has 4.5.0 and fedora14 has 4.5.1
>>
>> OK, so fedora14 is the fast one (4.5.1) and opensuse11.3 is the slow
>> one (4.5.0), correct?
>
> And does commit c7a3786030 help? This commit (from Peter Zijlstra)
> tidied up RCU kthreads' scheduler interactions. The patch is below,
> though it is probably more convenient to pull it from the rcu/next
> branch of:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-2.6-rcu.git
>

[ 337.132517] INFO: task rcun0:8 blocked for more than 120 seconds.
[ 337.133238] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.160396] rcun0 D 0000000000000000 0 8 2 0x00000000
[ 337.161232] ffff882070d3fe90 0000000000000046 ffff882070d3e000 0000000000004000
[ 337.161291] 00000000001d1f80 ffff882070d3ffd8 00000000001d1f80 ffff882070d3ffd8
[ 337.161348] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff882070d422b0
[ 337.161404] Call Trace:
[ 337.161433] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.161459] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.161486] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.161512] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.161533] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.161558] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.161584] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.161606] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.161627] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.161645] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.161651] no locks held by rcun0/8.
[ 337.161723] INFO: task rcun3:171 blocked for more than 120 seconds.
[ 337.161729] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.161736] rcun3 D 0000000000000000 0 171 2 0x00000000
[ 337.161748] ffff8820705bfe90 0000000000000046 ffff8820705be000 0000000000004000
[ 337.161786] 00000000001d1f80 ffff8820705bffd8 00000000001d1f80 ffff8820705bffd8
[ 337.161825] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff8820705ca2b0
[ 337.161863] Call Trace:
[ 337.161879] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.161895] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.161913] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.161930] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.161947] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.161963] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.161979] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.161995] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.162011] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.162026] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.162032] no locks held by rcun3/171.
[ 337.162110] INFO: task rcun5:333 blocked for more than 120 seconds.
[ 337.162117] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.162123] rcun5 D 0000000000000000 0 333 2 0x00000000
[ 337.162134] ffff882070079e90 0000000000000046 ffff882070078000 0000000000004000
[ 337.162173] 00000000001d1f80 ffff882070079fd8 00000000001d1f80 ffff882070079fd8
[ 337.162213] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff882070070000
[ 337.162250] Call Trace:
[ 337.162265] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.162282] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.162299] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.162316] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.162333] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.162349] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.162366] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.162382] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.162399] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.162415] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.162421] no locks held by rcun5/333.
[ 337.162469] INFO: task rcun6:414 blocked for more than 120 seconds.
[ 337.162475] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.162481] rcun6 D 0000000000000000 0 414 2 0x00000000
[ 337.162493] ffff8820701b3e90 0000000000000046 ffff8820701b2000 0000000000004000
[ 337.162532] 00000000001d1f80 ffff8820701b3fd8 00000000001d1f80 ffff8820701b3fd8
[ 337.162571] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff8820701ac560
[ 337.162610] Call Trace:
[ 337.162625] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.162640] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.162659] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.162676] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.162692] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.162709] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.162726] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.162741] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.162757] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.162773] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.162779] no locks held by rcun6/414.
[ 337.162816] INFO: task rcun7:495 blocked for more than 120 seconds.
[ 337.162822] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.162828] rcun7 D 0000000000000000 0 495 2 0x00000000
[ 337.162839] ffff8820703d1e90 0000000000000046 ffff8820703d0000 0000000000004000
[ 337.162880] 00000000001d1f80 ffff8820703d1fd8 00000000001d1f80 ffff8820703d1fd8
[ 337.162919] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff8820703ca2b0
[ 337.162957] Call Trace:
[ 337.162973] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.162989] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.163006] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.163022] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.163039] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.163055] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.163072] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.163087] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.163104] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.163120] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.163125] no locks held by rcun7/495.
[ 337.163166] INFO: task rcun8:576 blocked for more than 120 seconds.
[ 337.163172] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.163178] rcun8 D 0000000000000000 0 576 2 0x00000000
[ 337.163190] ffff881fff913e90 0000000000000046 ffff881fff912000 0000000000004000
[ 337.163231] 00000000001d1f80 ffff881fff913fd8 00000000001d1f80 ffff881fff913fd8
[ 337.163271] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff881fff90a2b0
[ 337.163309] Call Trace:
[ 337.163324] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.163340] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.163358] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.163375] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.163392] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.163409] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.163425] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.163440] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.163457] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.163473] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.163479] no locks held by rcun8/576.
[ 337.163558] INFO: task rcun10:738 blocked for more than 120 seconds.
[ 337.163564] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
[ 337.163570] rcun10 D 0000000000000000 0 738 2 0x00000000
[ 337.163582] ffff881fffbb5e90 0000000000000046 ffff881fffbb4000 0000000000004000
[ 337.163620] 00000000001d1f80 ffff881fffbb5fd8 00000000001d1f80 ffff881fffbb5fd8
[ 337.163659] 0000000000004000 00000000001d1f80 ffff882070d18000 ffff881fffbba2b0
[ 337.163697] Call Trace:
[ 337.163712] [<ffffffff810afab6>] ? __lock_release+0x166/0x16f
[ 337.163728] [<ffffffff81c1dae1>] ? _raw_spin_unlock_irqrestore+0x3f/0x46
[ 337.163744] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.163760] [<ffffffff810add8a>] ? trace_hardirqs_on+0xd/0xf
[ 337.163777] [<ffffffff810ce633>] ? rcu_cpu_kthread_should_stop+0x137/0x137
[ 337.163793] [<ffffffff81099e41>] kthread+0x8c/0xa8
[ 337.163810] [<ffffffff81c257d4>] kernel_thread_helper+0x4/0x10
[ 337.163826] [<ffffffff81c1dd80>] ? retint_restore_args+0xe/0xe
[ 337.163842] [<ffffffff81099db5>] ? __init_kthread_worker+0x5b/0x5b
[ 337.163857] [<ffffffff81c257d0>] ? gs_change+0xb/0xb
[ 337.163863] no locks held by rcun10/738.
--
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