linux-kernel - Re: Question on lockdep and MAX_LOCK

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Date:	Tue, 5 Feb 2013 23:26:11 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Ben Greear <greearb@...delatech.com>
Cc:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: Question on lockdep and MAX_LOCK_DEPTH

On Tue, Feb 05, 2013 at 05:10:37PM -0800, Ben Greear wrote:
> 
> 
> ===============================
> [ INFO: suspicious RCU usage. ]
> 3.7.6+ #4 Tainted: G         C O
> -------------------------------
> /home/greearb/git/linux-3.7.dev.y/kernel/rcutree.c:360 Illegal idle entry in RCU read-side critical section.!
> 
> other info that might help us debug this:
> 
> 
> RCU used illegally from idle CPU!
> rcu_scheduler_active = 1, debug_locks = 1
> RCU used illegally from extended quiescent state!
> 1 lock held by swapper/1/0:
>  #0:  (rcu_read_lock){.+.+..}, at: [<ffffffff81489632>] rcu_read_lock+0x0/0x6f
> 
> stack backtrace:
> Pid: 0, comm: swapper/1 Tainted: G         C O 3.7.6+ #4
> Call Trace:
>  <IRQ>  [<ffffffff810cecbd>] lockdep_rcu_suspicious+0xfc/0x105
>  [<ffffffff810fe146>] rcu_eqs_enter_common+0xef/0x178
>  [<ffffffff810fe24e>] rcu_irq_exit+0x7f/0xb0
>  [<ffffffff8108edf5>] irq_exit+0xc0/0xcc
>  [<ffffffff8100b635>] do_IRQ+0x97/0xae
>  [<ffffffff815543b2>] common_interrupt+0x72/0x72
>  <EOI>  [<ffffffff81011082>] ? mwait_idle+0x77/0x9f
>  [<ffffffff81011079>] ? mwait_idle+0x6e/0x9f
>  [<ffffffff81011379>] cpu_idle+0x68/0xbc
>  [<ffffffff8154ce84>] start_secondary+0x1fc/0x203

BTW, did the above error only happen when you added the dump of the
locks, or was it always there? Is this the bug you were trying to debug?

-- Steve

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