Deadlock between tasklist_lock and dcache_lock

[Manfred Spraul]

__unhash_process acquires the dcache_lock while holding the tasklist_lock 
for writing. AFAICS this can deadlock:

CPU1:
	[ in release_task() ]
	write_lock_irq(&tasklist_lock);
	__unhash_process()
	
CPU2:
	spin_lock(&dcache_lock);
	<interrupt>
	read_lock(&tasklist_lock);, // e.g. for signal delivery
	** spins, lock held by cpu 1 for writing.

CPU1:
	[ within __unhash_process() ]
	spin_lock(&dcache_lock);
	** spins, lock held by CPU2

Probably the callers of __unhash_process must acquire the dcache_lock 
before write_lock_irq(&tasklist_lock).

Any other ideas how to fix the deadlock?
--
	Manfred