Shrink task_struct if CONFIG_FUTEX=n

robust_list, compat_robust_list, pi_state_list, pi_state_cache are
really used if futexes are on.
Signed-off-by: Alexey Dobriyan <adobriyan@sw.ru>
Acked-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/sched.h

@@ -1132,13 +1132,14 @@ struct task_struct {
 	int cpuset_mems_generation;
 	int cpuset_mem_spread_rotor;
 #endif
+#ifdef CONFIG_FUTEX
 	struct robust_list_head __user *robust_list;
 #ifdef CONFIG_COMPAT
 	struct compat_robust_list_head __user *compat_robust_list;
 #endif
 	struct list_head pi_state_list;
 	struct futex_pi_state *pi_state_cache;
-
+#endif
 	atomic_t fs_excl;	/* holding fs exclusive resources */
 	struct rcu_head rcu;
 

kernel/exit.c

@@ -947,11 +947,13 @@ fastcall NORET_TYPE void do_exit(long code)
 		exit_itimers(tsk->signal);
 	}
 	acct_collect(code, group_dead);
+#ifdef CONFIG_FUTEX
 	if (unlikely(tsk->robust_list))
 		exit_robust_list(tsk);
-#if defined(CONFIG_FUTEX) && defined(CONFIG_COMPAT)
+#ifdef CONFIG_COMPAT
 	if (unlikely(tsk->compat_robust_list))
 		compat_exit_robust_list(tsk);
+#endif
 #endif
 	if (group_dead)
 		tty_audit_exit();
@@ -987,6 +989,7 @@ fastcall NORET_TYPE void do_exit(long code)
 	mpol_free(tsk->mempolicy);
 	tsk->mempolicy = NULL;
 #endif
+#ifdef CONFIG_FUTEX
 	/*
 	 * This must happen late, after the PID is not
 	 * hashed anymore:
@@ -995,6 +998,7 @@ fastcall NORET_TYPE void do_exit(long code)
 		exit_pi_state_list(tsk);
 	if (unlikely(current->pi_state_cache))
 		kfree(current->pi_state_cache);
+#endif
 	/*
 	 * Make sure we are holding no locks:
 	 */

kernel/fork.c

@@ -1156,13 +1156,14 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	 * Clear TID on mm_release()?
 	 */
 	p->clear_child_tid = (clone_flags & CLONE_CHILD_CLEARTID) ? child_tidptr: NULL;
+#ifdef CONFIG_FUTEX
 	p->robust_list = NULL;
 #ifdef CONFIG_COMPAT
 	p->compat_robust_list = NULL;
 #endif
 	INIT_LIST_HEAD(&p->pi_state_list);
 	p->pi_state_cache = NULL;
-
+#endif
 	/*
 	 * sigaltstack should be cleared when sharing the same VM
 	 */