signal: make may_ptrace_stop() return bool

may_ptrace_stop() already behaves like a boolean function.  Let's actually
declare it as such too.

Link: http://lkml.kernel.org/r/20180602103653.18181-4-christian@brauner.io
Signed-off-by: Christian Brauner <christian@brauner.io>
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: James Morris <james.morris@microsoft.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephen Smalley <sds@tycho.nsa.gov>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -1875,10 +1875,10 @@ static void do_notify_parent_cldstop(struct task_struct *tsk,
 	spin_unlock_irqrestore(&sighand->siglock, flags);
 }
 
-static inline int may_ptrace_stop(void)
+static inline bool may_ptrace_stop(void)
 {
 	if (!likely(current->ptrace))
-		return 0;
+		return false;
 	/*
 	 * Are we in the middle of do_coredump?
 	 * If so and our tracer is also part of the coredump stopping
@@ -1894,9 +1894,9 @@ static inline int may_ptrace_stop(void)
 	 */
 	if (unlikely(current->mm->core_state) &&
 	    unlikely(current->mm == current->parent->mm))
-		return 0;
+		return false;
 
-	return 1;
+	return true;
 }
 
 /*