mmu_hash_lock deadlock causes kernel stuck at 2.6.21 SMP powerpc 32bit

[Benjamin Herrenschmidt]

On Sun, 2008-03-30 at 14:28 -0700, Gaash Hazan wrote:
> To verify the theory, hash_page_sync() was wrapped
> with interrupts disabled code and problem never
> occurred again. Of course this is temporary workaround
> as there are several places needed to be fixed.

It is definitely a bug in hash_page_sync() which should
clear MSR:EE while holding the lock.

I'll do a patch.

Thanks for finding that out !

Cheers,
Ben.