[PATCH] cleanup __exit_signal->cleanup_sighand path

Move 'tsk->sighand = NULL' from cleanup_sighand() to __exit_signal().  This
makes the exit path more understandable and allows us to do
cleanup_sighand() outside of ->siglock protected section.
Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

include/linux/sched.h

@@ -1151,7 +1151,7 @@ extern void exit_thread(void);
 
 extern void exit_files(struct task_struct *);
 extern void __cleanup_signal(struct signal_struct *);
-extern void cleanup_sighand(struct task_struct *);
+extern void __cleanup_sighand(struct sighand_struct *);
 extern void exit_itimers(struct signal_struct *);
 
 extern NORET_TYPE void do_group_exit(int);

kernel/exit.c

@@ -114,10 +114,11 @@ static void __exit_signal(struct task_struct *tsk)
 	__unhash_process(tsk);
 
 	tsk->signal = NULL;
-	cleanup_sighand(tsk);
+	tsk->sighand = NULL;
 	spin_unlock(&sighand->siglock);
 	rcu_read_unlock();
 
+	__cleanup_sighand(sighand);
 	clear_tsk_thread_flag(tsk,TIF_SIGPENDING);
 	flush_sigqueue(&tsk->pending);
 	if (sig) {

kernel/fork.c

@@ -803,12 +803,8 @@ static inline int copy_sighand(unsigned long clone_flags, struct task_struct * t
 	return 0;
 }
 
-void cleanup_sighand(struct task_struct *tsk)
+void __cleanup_sighand(struct sighand_struct *sighand)
 {
-	struct sighand_struct * sighand = tsk->sighand;
-
-	/* Ok, we're done with the signal handlers */
-	tsk->sighand = NULL;
 	if (atomic_dec_and_test(&sighand->count))
 		kmem_cache_free(sighand_cachep, sighand);
 }
@@ -1233,7 +1229,7 @@ bad_fork_cleanup_mm:
 bad_fork_cleanup_signal:
 	cleanup_signal(p);
 bad_fork_cleanup_sighand:
-	cleanup_sighand(p);
+	__cleanup_sighand(p->sighand);
 bad_fork_cleanup_fs:
 	exit_fs(p); /* blocking */
 bad_fork_cleanup_files: