Re: Question on lockdep and MAX_LOCK_DEPTH

[Ben Greear <greearb@candelatech.com>]

On 02/05/2013 08:26 PM, Steven Rostedt wrote:
> 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?

It's often there, at least..and was from the beginning, and I
am interested in debugging it.

Thanks,
Ben



-- 
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc  http://www.candelatech.com