um: Get rid of thread_struct->saved_task

As we have a sane show_stack() now, we can drop
the ->saved_task hack.
Signed-off-by: Richard Weinberger <richard@nod.at>

arch/um/drivers/mconsole_kern.c

@@ -645,11 +645,9 @@ void mconsole_sysrq(struct mc_request *req)
 
 static void stack_proc(void *arg)
 {
-	struct task_struct *from = current, *to = arg;
+	struct task_struct *task = arg;
 
-	to->thread.saved_task = from;
-	rcu_user_hooks_switch(from, to);
-	switch_to(from, to, from);
+	show_stack(task, NULL);
 }
 
 /*

arch/um/include/asm/processor-generic.h

@@ -19,7 +19,6 @@ struct task_struct;
 struct mm_struct;
 
 struct thread_struct {
-	struct task_struct *saved_task;
 	struct pt_regs regs;
 	struct pt_regs *segv_regs;
 	int singlestep_syscall;

arch/um/kernel/process.c

@@ -82,19 +82,8 @@ void *__switch_to(struct task_struct *from, struct task_struct *to)
 	to->thread.prev_sched = from;
 	set_current(to);
 
-	do {
-		current->thread.saved_task = NULL;
-
-		switch_threads(&from->thread.switch_buf,
-			       &to->thread.switch_buf);
-
-		arch_switch_to(current);
-
-		if (current->thread.saved_task)
-			show_regs(&(current->thread.regs));
-		to = current->thread.saved_task;
-		from = current;
-	} while (current->thread.saved_task);
+	switch_threads(&from->thread.switch_buf, &to->thread.switch_buf);
+	arch_switch_to(current);
 
 	return current->thread.prev_sched;
 }