sched, autogroup: Fix reference leak

The cgroup exit mess also uncovered a struct autogroup reference leak.
copy_process() was simply freeing vs putting the signal_struct,
stranding a reference.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Oleg Nesterov <oleg@redhat.com>
LKML-Reference: <1293784350.6839.2.camel@marge.simson.net>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

kernel/fork.c

@@ -1317,7 +1317,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	}
 bad_fork_cleanup_signal:
 	if (!(clone_flags & CLONE_THREAD))
-		free_signal_struct(p->signal);
+		put_signal_struct(p->signal);
 bad_fork_cleanup_sighand:
 	__cleanup_sighand(p->sighand);
 bad_fork_cleanup_fs: