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

[Frederic Weisbecker]

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 ?
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