linux-kernel - Re: [RFC PATCH] Fix abnormal rcu dynticks_nesting values related to async page fault

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Date:	Tue, 27 Nov 2012 16:34:30 +0100
From:	Frederic Weisbecker <fweisbec@...il.com>
To:	Gleb Natapov <gleb@...hat.com>
Cc:	Li Zhong <zhong@...ux.vnet.ibm.com>,
	linux-next list <linux-next@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, paulmck@...ux.vnet.ibm.com,
	sasha.levin@...cle.com, avi@...hat.com
Subject: Re: [RFC PATCH] Fix abnormal rcu dynticks_nesting values related to
 async page fault

2012/11/27 Gleb Natapov <gleb@...hat.com>:
> On Tue, Nov 27, 2012 at 01:15:25PM +0800, Li Zhong wrote:
>> @@ -247,10 +247,17 @@ do_async_page_fault(struct pt_regs *regs, unsigned long error_code)
>>               break;
>>       case KVM_PV_REASON_PAGE_NOT_PRESENT:
>>               /* page is swapped out by the host. */
>> -             rcu_irq_enter();
>> +             if (is_idle_task(current) && rcu_is_cpu_idle())
>> +                     rcu_idle_exit();
>> +             else
>> +                     rcu_user_exit();
>> +
>>               exit_idle();
>>               kvm_async_pf_task_wait((u32)read_cr2());
>> -             rcu_irq_exit();
>> +
>> +             if (is_idle_task(current) && rcu_is_cpu_idle())
>> +                     rcu_idle_enter();
>> +
>>               break;
>>       case KVM_PV_REASON_PAGE_READY:
>>               rcu_irq_enter();
> Those rcu_irq_enter()/rcu_irq_exit() were introduced by commit
> c5e015d4949aa665 "KVM guest: exit idleness when handling
> KVM_PV_REASON_PAGE_NOT_PRESENT",

Ah!

    $ git name-rev  c5e015d4949aa665
    c5e015d4949aa665 remotes/tip/core/locking~3^2

Ok so that's not in -rcu. That's why I missed it.
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