powerpc/kernel: Rename copy_thread() 'arg' argument to 'kthread_arg'

The 'arg' argument to copy_thread() is only ever used when forking a new
kernel thread. Hence, rename it to 'kthread_arg' for clarity.
Signed-off-by: Alex Dowad <alexinbeijing@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/kernel/process.c

@@ -1114,8 +1114,11 @@ static void setup_ksp_vsid(struct task_struct *p, unsigned long sp)
  */
 extern unsigned long dscr_default; /* defined in arch/powerpc/kernel/sysfs.c */
 
+/*
+ * Copy architecture-specific thread state
+ */
 int copy_thread(unsigned long clone_flags, unsigned long usp,
-		unsigned long arg, struct task_struct *p)
+		unsigned long kthread_arg, struct task_struct *p)
 {
 	struct pt_regs *childregs, *kregs;
 	extern void ret_from_fork(void);
@@ -1127,6 +1130,7 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 	sp -= sizeof(struct pt_regs);
 	childregs = (struct pt_regs *) sp;
 	if (unlikely(p->flags & PF_KTHREAD)) {
+		/* kernel thread */
 		struct thread_info *ti = (void *)task_stack_page(p);
 		memset(childregs, 0, sizeof(struct pt_regs));
 		childregs->gpr[1] = sp + sizeof(struct pt_regs);
@@ -1137,11 +1141,12 @@ int copy_thread(unsigned long clone_flags, unsigned long usp,
 		clear_tsk_thread_flag(p, TIF_32BIT);
 		childregs->softe = 1;
 #endif
-		childregs->gpr[15] = arg;
+		childregs->gpr[15] = kthread_arg;
 		p->thread.regs = NULL;	/* no user register state */
 		ti->flags |= _TIF_RESTOREALL;
 		f = ret_from_kernel_thread;
 	} else {
+		/* user thread */
 		struct pt_regs *regs = current_pt_regs();
 		CHECK_FULL_REGS(regs);
 		*childregs = *regs;