2009/8/7 Peter Zijlstra [off-list ref]:

On Fri, 2009-08-07 at 09:46 -0500, Clark Williams wrote:

quoted

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
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