signal: Move set_notify_signal and clear_notify_signal into sched/signal.h

The header tracehook.h is no place for code to live. The functions
set_notify_signal and clear_notify_signal are not about signals. They
are about interruptions that act like signals. The fundamental signal
primitives wind up calling set_notify_signal and clear_notify_signal.
Which means they need to be maintained with the signal code.

Since set_notify_signal and clear_notify_signal must be maintained
with the signal subsystem move them into sched/signal.h and claim them
as part of the signal subsystem.

Reviewed-by: Kees Cook <[e-mail]>
Link: https://lkml.kernel.org/r/[e-mail]
Signed-off-by: "Eric W. Biederman" <[e-mail]>

include/linux/sched/signal.h

···
 extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type);
 extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *);
 
+static inline void clear_notify_signal(void)
+{
+	clear_thread_flag(TIF_NOTIFY_SIGNAL);
+	smp_mb__after_atomic();
+}
+
+/*
+ * Called to break out of interruptible wait loops, and enter the
+ * exit_to_user_mode_loop().
+ */
+static inline void set_notify_signal(struct task_struct *task)
+{
+	if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
+	    !wake_up_state(task, TASK_INTERRUPTIBLE))
+		kick_process(task);
+}
+
 static inline int restart_syscall(void)
 {
 	set_tsk_thread_flag(current, TIF_SIGPENDING);

include/linux/tracehook.h

···
 	rseq_handle_notify_resume(NULL, regs);
 }
 
-static inline void clear_notify_signal(void)
-{
-	clear_thread_flag(TIF_NOTIFY_SIGNAL);
-	smp_mb__after_atomic();
-}
-
-/*
- * Called to break out of interruptible wait loops, and enter the
- * exit_to_user_mode_loop().
- */
-static inline void set_notify_signal(struct task_struct *task)
-{
-	if (!test_and_set_tsk_thread_flag(task, TIF_NOTIFY_SIGNAL) &&
-	    !wake_up_state(task, TASK_INTERRUPTIBLE))
-		kick_process(task);
-}
-
 #endif	/* <linux/tracehook.h> */