task_work: Introduce task_work_pending

Wrap the test of task->task_works in a helper function to make
it clear what is being tested.

All of the other readers of task->task_work use READ_ONCE and this is
even necessary on current as other processes can update
task->task_work.  So for consistency I have added READ_ONCE into
task_work_pending.

Reviewed-by: Kees Cook <keescook@chromium.org>
Link: https://lkml.kernel.org/r/20220309162454.123006-7-ebiederm@xmission.com
Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>

include/linux/task_work.h

@@ -19,6 +19,11 @@ enum task_work_notify_mode {
 	TWA_SIGNAL,
 };
 
+static inline bool task_work_pending(struct task_struct *task)
+{
+	return READ_ONCE(task->task_works);
+}
+
 int task_work_add(struct task_struct *task, struct callback_head *twork,
 			enum task_work_notify_mode mode);