exit: kill the pointless __exit_signal()->clear_tsk_thread_flag(TIF_SIGPENDING)

It predates the git history and most probably it was never needed. It
doesn't really hurt, but it looks confusing because its purpose is not
clear at all.

release_task(p) is called when this task has already passed exit_notify()
so signal_pending(p) == T shouldn't make any difference.

And even _if_ there were a subtle reason to clear TIF_SIGPENDING after
exit_notify(), this clear_tsk_thread_flag() can't help anyway.  If the
exiting task is a group leader or if it is ptraced, release_task() will
be likely called when this task has already done its last schedule() from
do_task_dead().

Signed-off-by: Oleg Nesterov <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Acked-by: Frederic Weisbecker <[email protected]>
Signed-off-by: Christian Brauner <[email protected]>

Author: oleg-nesterov

kernel/exit.c

@@ -204,7 +204,6 @@ static void __exit_signal(struct task_struct *tsk)
 	spin_unlock(&sighand->siglock);
 
 	__cleanup_sighand(sighand);
-	clear_tsk_thread_flag(tsk, TIF_SIGPENDING);
 	if (group_dead)
 		tty_kref_put(tty);
 }