linux-kernel - Re: [GIT PULL rcu/next] rcu commits for 2.6.40

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Message-ID: <4DD58F90.4090506@kernel.org>
Date:	Thu, 19 May 2011 14:45:52 -0700
From:	Yinghai Lu <yinghai@...nel.org>
To:	Frederic Weisbecker <fweisbec@...il.com>
CC:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>
Subject: Re: [GIT PULL rcu/next] rcu commits for 2.6.40

On 05/19/2011 02:15 PM, Frederic Weisbecker wrote:
> On Thu, May 19, 2011 at 12:51:26PM -0700, Yinghai Lu wrote:
>> [   85.194797]   <idle>-0       0d... 85152953us : rcu_irq_enter: 1 49
>> [   85.194808]   <idle>-0       0dN.. 85153081us : <stack trace>
>> [   85.194809]  => rcu_irq_exit
>> [   85.194810]  => irq_exit
>> [   85.194811]  => smp_apic_timer_interrupt
>> [   85.194812]  => apic_timer_interrupt
>> [   85.194813]  => cpu_idle
>> [   85.194813]  => rest_init
>> [   85.194814]  => start_kernel
>> [   85.194815]  => x86_64_start_reservations
> 
> So it's the dynticks_nesting going crazy. As if we had rcu_irq_enter()
> without rcu_irq_exit().
> 
> I see you have CONFIG_DEBUG_LOCKING_API_SELFTESTS=y
> and the locking api selftest is doing a strange thing: if we look
> at HARDIRQ_ENTER(), it calls irq_enter(), but HARDIRQ_EXIT() only
> calls __irq_exit(). Which means it lacks the rcu_irq_exit().
> 
> So, if I understood correctly the thing there, some selftests simulating
> the hardirq context are unbalancing the rcu state.
> 
> Does that help if you unset CONFIG_DEBUG_LOCKING_API_SELFTESTS ?


yes, after unset that, no warning and delay...

Thanks
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