linux-kernel - Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6

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Message-ID: <500F0BAB.7060001@gmail.com>
Date:	Tue, 24 Jul 2012 22:55:07 +0200
From:	Sasha Levin <levinsasha928@...il.com>
To:	paulmck@...ux.vnet.ibm.com
CC:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: rcu: INFO: rcu_preempt detected stalls on CPUs/tasks on v3.6

On 07/24/2012 07:40 PM, Paul E. McKenney wrote:
> The interrupt flag is zero, so interrupts are disabled.  So my question
> to you is "Why did do_pageattr_test() or one of the functions it called
> disable interrupts for more than one hundred thousand jiffies?"
> 
> I can't see where it is disabling interrupts, but the EFLAGS register
> above does indicate that they are disabled.  Or is this something useless
> that is just telling us that receiving the NMI disabled interrupts?

Doesn't the stack of CPU1 show that it's currently handling an interrupt:

[  215.026612] Call Trace:
[  215.026612]  <IRQ>
[  215.026612]  [<ffffffff81095d07>] native_apic_msr_eoi_write+0x27/0x30
[  215.026612]  [<ffffffff810901c4>] smp_apic_timer_interrupt+0x34/0xa0
[  215.026612]  [<ffffffff8369c4af>] apic_timer_interrupt+0x6f/0x80
[  215.026612]  <EOI>

Or am I reading that wrong?

In that case, it had nothing to do with pageattr which just happened to be on the stack at that time.
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