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Message-ID: <20120403105226.GF14939@redhat.com>
Date:	Tue, 3 Apr 2012 13:52:26 +0300
From:	Gleb Natapov <gleb@...hat.com>
To:	Sasha Levin <levinsasha928@...il.com>
Cc:	Avi Kivity <avi@...hat.com>, Marcelo Tosatti <mtosatti@...hat.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	kvm <kvm@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>
Subject: Re: kvm: RCU warning in async pf

On Mon, Apr 02, 2012 at 08:54:32PM -0400, Sasha Levin wrote:
> Hi all,
> 
> I got the spew at the bottom of the mail in a KVM guest using the KVM tools and running trinity.
> 
> I'm not quite sure how default_idle managed to trigger a pagefault, so that part looks odd to me.
> 
This is not regular page fault. This is async page fault that tells the
guest that a page, previously swapped out by hypervisor, is now swapped
back in and it can happen while vcpu is idle. The code does not leave
idle state properly though. We probably need to call rcu_irq_enter()
there. Will look into it.

> [12140.220507] ===============================
> [12140.220507] [ INFO: suspicious RCU usage. ]
> [12140.220507] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.220507] -------------------------------
> [12140.220507] include/linux/rcupdate.h:729 rcu_read_lock() used illegally while idle!
> [12140.220507] 
> [12140.220507] other info that might help us debug this:
> [12140.220507] 
> [12140.220507] 
> [12140.220507] RCU used illegally from idle CPU!
> [12140.220507] rcu_scheduler_active = 1, debug_locks = 1
> [12140.220507] RCU used illegally from extended quiescent state!
> [12140.220507] 4 locks held by swapper/1/0:
> [12140.253991]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.253991]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.253991]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.253991]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810f3c80>] select_task_rq_fair+0xb0/0x5c0
> [12140.253991] 
> [12140.253991] stack backtrace:
> [12140.253991] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.253991] Call Trace:
> [12140.253991]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.253991]  [<ffffffff810f3ce5>] select_task_rq_fair+0x115/0x5c0
> [12140.253991]  [<ffffffff810f3c80>] ? select_task_rq_fair+0xb0/0x5c0
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec561>] try_to_wake_up+0x191/0x290
> [12140.253991]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.253991]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.253991]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.253991]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.253991]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.253991]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.253991]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.253991]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.253991]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.253991]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.253991]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.253991]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.253991]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.253991]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.253991]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.253991]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> [12140.253991] 
> [12140.253991] ===============================
> [12140.253991] [ INFO: suspicious RCU usage. ]
> [12140.253991] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.253991] -------------------------------
> [12140.253991] kernel/sched/fair.c:2716 suspicious rcu_dereference_check() usage!
> [12140.253991] 
> [12140.253991] other info that might help us debug this:
> [12140.253991] 
> [12140.253991] 
> [12140.253991] RCU used illegally from idle CPU!
> [12140.253991] rcu_scheduler_active = 1, debug_locks = 1
> [12140.253991] RCU used illegally from extended quiescent state!
> [12140.253991] 4 locks held by swapper/1/0:
> [12140.253991]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.253991]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.253991]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.253991]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810f3c80>] select_task_rq_fair+0xb0/0x5c0
> [12140.253991] 
> [12140.253991] stack backtrace:
> [12140.253991] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.253991] Call Trace:
> [12140.253991]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.253991]  [<ffffffff810f3d4c>] select_task_rq_fair+0x17c/0x5c0
> [12140.253991]  [<ffffffff810f3c80>] ? select_task_rq_fair+0xb0/0x5c0
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec561>] try_to_wake_up+0x191/0x290
> [12140.253991]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.253991]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.253991]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.253991]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.253991]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.253991]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.253991]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.253991]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.253991]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.253991]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.253991]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.253991]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.253991]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.253991]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.253991]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.253991]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> [12140.253991] 
> [12140.253991] ===============================
> [12140.253991] [ INFO: suspicious RCU usage. ]
> [12140.253991] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.253991] -------------------------------
> [12140.253991] kernel/sched/fair.c:2660 suspicious rcu_dereference_check() usage!
> [12140.253991] 
> [12140.253991] other info that might help us debug this:
> [12140.253991] 
> [12140.253991] 
> [12140.253991] RCU used illegally from idle CPU!
> [12140.253991] rcu_scheduler_active = 1, debug_locks = 1
> [12140.253991] RCU used illegally from extended quiescent state!
> [12140.253991] 4 locks held by swapper/1/0:
> [12140.253991]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.253991]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.253991]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.253991]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810f3c80>] select_task_rq_fair+0xb0/0x5c0
> [12140.253991] 
> [12140.253991] stack backtrace:
> [12140.253991] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.253991] Call Trace:
> [12140.253991]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.253991]  [<ffffffff810f062f>] select_idle_sibling+0xaf/0x1c0
> [12140.253991]  [<ffffffff810f3f51>] select_task_rq_fair+0x381/0x5c0
> [12140.253991]  [<ffffffff810f3c80>] ? select_task_rq_fair+0xb0/0x5c0
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec561>] try_to_wake_up+0x191/0x290
> [12140.253991]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.253991]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.253991]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.253991]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.253991]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.253991]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.253991]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.253991]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.253991]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.253991]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.253991]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.253991]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.253991]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.253991]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.253991]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.253991]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> [12140.253991] 
> [12140.253991] ===============================
> [12140.253991] [ INFO: suspicious RCU usage. ]
> [12140.253991] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.253991] -------------------------------
> [12140.253991] include/linux/rcupdate.h:750 rcu_read_unlock() used illegally while idle!
> [12140.253991] 
> [12140.253991] other info that might help us debug this:
> [12140.253991] 
> [12140.253991] 
> [12140.253991] RCU used illegally from idle CPU!
> [12140.253991] rcu_scheduler_active = 1, debug_locks = 1
> [12140.253991] RCU used illegally from extended quiescent state!
> [12140.253991] 4 locks held by swapper/1/0:
> [12140.253991]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.253991]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.253991]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.253991]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810f3c80>] select_task_rq_fair+0xb0/0x5c0
> [12140.253991] 
> [12140.253991] stack backtrace:
> [12140.253991] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.253991] Call Trace:
> [12140.253991]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.253991]  [<ffffffff810f412a>] select_task_rq_fair+0x55a/0x5c0
> [12140.253991]  [<ffffffff810f3c80>] ? select_task_rq_fair+0xb0/0x5c0
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.253991]  [<ffffffff810ec561>] try_to_wake_up+0x191/0x290
> [12140.253991]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.253991]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.253991]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.253991]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.253991]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.253991]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.253991]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.253991]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.253991]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.253991]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.253991]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.253991]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.253991]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.253991]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.253991]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.253991]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> [12140.623131] 
> [12140.623131] ===============================
> [12140.623131] [ INFO: suspicious RCU usage. ]
> [12140.623131] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.623131] -------------------------------
> [12140.623131] include/linux/rcupdate.h:729 rcu_read_lock() used illegally while idle!
> [12140.623131] 
> [12140.623131] other info that might help us debug this:
> [12140.623131] 
> [12140.623131] 
> [12140.623131] RCU used illegally from idle CPU!
> [12140.623131] rcu_scheduler_active = 1, debug_locks = 1
> [12140.623131] RCU used illegally from extended quiescent state!
> [12140.623131] 4 locks held by swapper/1/0:
> [12140.623131]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.623131]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.623131]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.623131]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810ea4c0>] ttwu_stat+0x50/0x230
> [12140.623131] 
> [12140.623131] stack backtrace:
> [12140.623131] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.623131] Call Trace:
> [12140.623131]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.623131]  [<ffffffff810ea537>] ttwu_stat+0xc7/0x230
> [12140.623131]  [<ffffffff810ea4c0>] ? ttwu_stat+0x50/0x230
> [12140.623131]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.623131]  [<ffffffff810ec62a>] try_to_wake_up+0x25a/0x290
> [12140.623131]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.623131]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.623131]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.623131]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.623131]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.623131]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.623131]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.623131]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.623131]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.623131]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.623131]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.623131]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.623131]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.623131]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.623131]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.623131]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> [12140.623131] 
> [12140.623131] ===============================
> [12140.623131] [ INFO: suspicious RCU usage. ]
> [12140.623131] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.623131] -------------------------------
> [12140.623131] kernel/sched/core.c:1375 suspicious rcu_dereference_check() usage!
> [12140.623131] 
> [12140.623131] other info that might help us debug this:
> [12140.623131] 
> [12140.623131] 
> [12140.623131] RCU used illegally from idle CPU!
> [12140.623131] rcu_scheduler_active = 1, debug_locks = 1
> [12140.623131] RCU used illegally from extended quiescent state!
> [12140.623131] 4 locks held by swapper/1/0:
> [12140.623131]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.623131]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.623131]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.623131]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810ea4c0>] ttwu_stat+0x50/0x230
> [12140.623131] 
> [12140.623131] stack backtrace:
> [12140.623131] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.623131] Call Trace:
> [12140.623131]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.623131]  [<ffffffff810ea5a8>] ttwu_stat+0x138/0x230
> [12140.623131]  [<ffffffff810ea4c0>] ? ttwu_stat+0x50/0x230
> [12140.623131]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.623131]  [<ffffffff810ec62a>] try_to_wake_up+0x25a/0x290
> [12140.623131]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.623131]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.623131]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.623131]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.623131]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.623131]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.623131]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.623131]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.623131]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.623131]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.623131]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.623131]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.623131]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.623131]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.623131]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.623131]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> [12140.623131] 
> [12140.623131] ===============================
> [12140.623131] [ INFO: suspicious RCU usage. ]
> [12140.623131] 3.4.0-rc1-next-20120402-sasha #46 Tainted: G        W   
> [12140.623131] -------------------------------
> [12140.623131] include/linux/rcupdate.h:750 rcu_read_unlock() used illegally while idle!
> [12140.623131] 
> [12140.623131] other info that might help us debug this:
> [12140.623131] 
> [12140.623131] 
> [12140.623131] RCU used illegally from idle CPU!
> [12140.623131] rcu_scheduler_active = 1, debug_locks = 1
> [12140.623131] RCU used illegally from extended quiescent state!
> [12140.623131] 4 locks held by swapper/1/0:
> [12140.623131]  #0:  (&(&async_pf_sleepers[i].lock)->rlock){..-...}, at: [<ffffffff8107cdc8>] kvm_async_pf_task_wake+0x48/0x130
> [12140.623131]  #1:  (&n.wq){......}, at: [<ffffffff810e200d>] __wake_up+0x2d/0x70
> [12140.623131]  #2:  (&p->pi_lock){-.-.-.}, at: [<ffffffff810ec404>] try_to_wake_up+0x34/0x290
> [12140.623131]  #3:  (rcu_read_lock){.+.+..}, at: [<ffffffff810ea4c0>] ttwu_stat+0x50/0x230
> [12140.623131] 
> [12140.623131] stack backtrace:
> [12140.623131] Pid: 0, comm: swapper/1 Tainted: G        W    3.4.0-rc1-next-20120402-sasha #46
> [12140.623131] Call Trace:
> [12140.623131]  [<ffffffff81114173>] lockdep_rcu_suspicious+0x113/0x130
> [12140.623131]  [<ffffffff810ea643>] ttwu_stat+0x1d3/0x230
> [12140.623131]  [<ffffffff810ea4c0>] ? ttwu_stat+0x50/0x230
> [12140.623131]  [<ffffffff810ec404>] ? try_to_wake_up+0x34/0x290
> [12140.623131]  [<ffffffff810ec62a>] try_to_wake_up+0x25a/0x290
> [12140.623131]  [<ffffffff81114850>] ? __lock_acquired+0x1c0/0x210
> [12140.623131]  [<ffffffff810ec66d>] default_wake_function+0xd/0x10
> [12140.623131]  [<ffffffff810d7208>] autoremove_wake_function+0x18/0x40
> [12140.623131]  [<ffffffff810e11e2>] __wake_up_common+0x52/0x90
> [12140.623131]  [<ffffffff810e200d>] ? __wake_up+0x2d/0x70
> [12140.623131]  [<ffffffff810e2023>] __wake_up+0x43/0x70
> [12140.623131]  [<ffffffff8107cb07>] apf_task_wake_one+0x87/0x90
> [12140.623131]  [<ffffffff8107cdf5>] kvm_async_pf_task_wake+0x75/0x130
> [12140.623131]  [<ffffffff8107d1e6>] do_async_page_fault+0x86/0xa0
> [12140.623131]  [<ffffffff82657a55>] async_page_fault+0x25/0x30
> [12140.623131]  [<ffffffff8107d626>] ? native_safe_halt+0x6/0x10
> [12140.623131]  [<ffffffff81116fed>] ? trace_hardirqs_on+0xd/0x10
> [12140.623131]  [<ffffffff8105857d>] default_idle+0x4d/0xa0
> [12140.623131]  [<ffffffff810582af>] cpu_idle+0x11f/0x180
> [12140.623131]  [<ffffffff8264b9e0>] ? setup_APIC_timer+0x88/0x8c
> [12140.623131]  [<ffffffff8264b004>] start_secondary+0xe1/0xe8
> 
> -- 
> 
> Sasha.

--
			Gleb.
--
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