[ARM PATCH] 1806/1: Adding barrier() to show_stack () for proper backtracing

Patch from Marc Singer

As suggested by Russell, we add a barrier() before returning from
stack_trace().  This was helpful when diagnosing a problem with a
kernel transition to user-space where the problem was a lack of
floating point support in the kernel.  Without this change, the
backtrace reported an error.

It is possible that this change has already been made.  I don't see it
in any of the applied patches that I can read.

arch/arm/kernel/traps.c

@@ -204,6 +204,7 @@ void show_stack(struct task_struct *tsk, unsigned long *sp)
 		asm("mov%? %0, fp" : "=r" (fp));
 
 	c_backtrace(fp, 0x10);
+	barrier();
 }
 
 spinlock_t die_lock = SPIN_LOCK_UNLOCKED;