tasks/fork: Remove unnecessary child->exit_state

A zombie task obviously can't fork(), remove the unnecessary
initialization of child->exit_state. It is zero anyway after
dup_task_struct().

Note: copy_process() is huge and it has a lot of chaotic
initializations, probably it makes sense to move them into the
new helper called by dup_task_struct().

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: David Laight <David.Laight@ACULAB.COM>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131113143612.GA10540@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

kernel/fork.c

@@ -1402,13 +1402,11 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 		p->tgid = p->pid;
 	}
 
-	p->pdeath_signal = 0;
-	p->exit_state = 0;
-
 	p->nr_dirtied = 0;
 	p->nr_dirtied_pause = 128 >> (PAGE_SHIFT - 10);
 	p->dirty_paused_when = 0;
 
+	p->pdeath_signal = 0;
 	INIT_LIST_HEAD(&p->thread_group);
 	p->task_works = NULL;