fix BUG: sleeping function called from invalid context at mm/slab.c:3044

Since unwind_frame_init_from_blocked_task() may be called from interrupt/in_atomic context, it needs to kmalloc() memory with GFP_ATOMIC instead of GFP_KERNEL.

This fixes this warning (ShowTasks called from sysrq handler):

BUG: sleeping function called from invalid context at mm/slab.c:3044
in_atomic(): 1, irqs_disabled(): 1, pid: 2119, name: miniruby
Backtrace:
 [<10132e78>] __might_sleep+0x4c/0x118
 [<1018f644>] kmem_cache_alloc+0x2c/0xb4
 [<1011bae0>] unwind_frame_init_from_blocked_task+0x30/0xa0
 [<1010fd3c>] parisc_show_stack+0x3c/0xac
 [<10132c7c>] show_state_filter+0x80/0xd8
 [<102f4074>] __handle_sysrq+0xd0/0x1b0
 [<102f9558>] receive_chars+0x22c/0x318
 [<102f9940>] serial8250_handle_port+0x40/0x88
 [<102f9a8c>] serial8250_interrupt+0x104/0x10c
 [<10161920>] handle_IRQ_event+0x44/0x94
 [<10161acc>] __do_IRQ+0x15c/0x1dc
 [<102c442c>] superio_interrupt+0x74/0xa8
 [<10161920>] handle_IRQ_event+0x44/0x94
 [<10161acc>] __do_IRQ+0x15c/0x1dc
 [<10110fb4>] do_cpu_irq_mask+0x90/0xbc
 [<10114068>] intr_return+0x0/0x4

index 6773c58..69dad5a 100644
@@ -372,7 +372,7 @@ void unwind_frame_init_from_blocked_task(struct unwind_frame_info *info, struct
 	struct pt_regs *r = &t->thread.regs;
 	struct pt_regs *r2;
 
-	r2 = kmalloc(sizeof(struct pt_regs), GFP_KERNEL);
+	r2 = kmalloc(sizeof(struct pt_regs), GFP_ATOMIC);
 	if (!r2)
 		return;
 	*r2 = *r;

that's right, it used to just allocate r2 but i introduced this bug when i killed some stack heavy things a while back.

applied, kyle

i knew there was a reason why this was a stack variable before... ;-) (of course, that is not ideal either)

randolph