[PATCH 4/4] task_work: simplify the usage in ptrace_notify() and get_signal_to_deliver()

ptrace_notify() and get_signal_to_deliver() do unnecessary things before task_work_run(). 1. smp_mb__after_clear_bit() is not needed, test_and_clear_bit() implies mb(). 2. And we do not need the barrier at all, in this case we only care about the "synchronous" works added by the task

[PATCH 4/4] task_work: simplify the usage in ptrace_notify() and get_signal_to_deliver()

ptrace_notify() and get_signal_to_deliver() do unnecessary things before task_work_run(). 1. smp_mb__after_clear_bit() is not needed, test_and_clear_bit() implies mb(). 2. And we do not need the barrier at all, in this case we only care about the synchronous works added by the task itself.