[PATCH] task_struct alignment fix

The recent slab alignment changes broke an unknown number of architectures
(parisc and x86_64 for sure) by causing task_structs to be insufficiently
aligned.

We need good alignemnt because architectures do things like dumping FP state
into the task_struct with instructions which require particular alignment (I
think).

So change the default alignment to L1_CACHE_BYTES, which is what we used to
have, via SLAB_HW_CACHE_ALIGN.

kernel/fork.c

@@ -211,7 +211,7 @@ void __init fork_init(unsigned long mempages)
 {
 #ifndef __HAVE_ARCH_TASK_STRUCT_ALLOCATOR
 #ifndef ARCH_MIN_TASKALIGN
-#define ARCH_MIN_TASKALIGN	0
+#define ARCH_MIN_TASKALIGN	L1_CACHE_BYTES
 #endif
 	/* create a slab on which task_structs can be allocated */
 	task_struct_cachep =