Re: [RT] Lockdep warning on boot with 2.6.31-rc5-rt1.1

[Ming Lei <tom.leiming@gmail.com>]

2009/8/7 Peter Zijlstra <peterz@infradead.org>:
> On Fri, 2009-08-07 at 09:46 -0500, Clark Williams wrote:
>> Peter,
>>
>> I'm getting this warning from lockdep when booting on my T60.
>>
>> The two addresses reported (0xffffffff812664a2 and 0xffffffff812664ae)
>> actually bracket one call to mutex_lock() in driver_attach() so I'm not
>> sure what the complaint is.
>>
>> Clark
>>
>> =============================================
>> [ INFO: possible recursive locking detected ]
>> 2.6.31-rc5-rt1.1 #37
>> ---------------------------------------------
>> swapper/1 is trying to acquire lock:
>>  (&dev->mutex){+.+...}, at: [<ffffffff812664ae>]
>> __driver_attach+0x48/0x81
>>
>> but task is already holding lock:
>>  (&dev->mutex){+.+...}, at: [<ffffffff812664a2>]
>> __driver_attach+0x3c/0x81
>>
>> other info that might help us debug this:
>> 1 lock held by swapper/1:
>>  #0:  (&dev->mutex){+.+...}, at: [<ffffffff812664a2>]
>> __driver_attach+0x3c/0x81
>
> Oh, that's tglx who's gone wild with sem->mutex conversions.

Maybe we can introduce some mutex interfaces which bypass lockdep validation
temporarily to allow driver core to convert to mutex from sema if lockdep
can't validate tree-structured lock orderings.

Thanks.

--
Lei Ming