signals: kill the obsolete sigdelset() and recalc_sigpending() in allow_signal()

allow_signal() does sigdelset(current->blocked) due to historic reason,
previously it could be called by a daemonize()'ed kthread, and
daemonize() played with current->blocked.

Now that daemonize() has gone away we can remove sigdelset() and
recalc_sigpending().  If a user really wants to unblock a signal, it
must use sigprocmask() or set_current_block() explicitely.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Al Viro <viro@ZenIV.linux.org.uk>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Geert Uytterhoeven <geert@linux-m68k.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Richard Weinberger <richard@nod.at>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/signal.c

@@ -3072,16 +3072,13 @@ COMPAT_SYSCALL_DEFINE4(rt_tgsigqueueinfo,
  */
 void allow_signal(int sig)
 {
-	spin_lock_irq(&current->sighand->siglock);
-	/* This is only needed for daemonize()'ed kthreads */
-	sigdelset(&current->blocked, sig);
 	/*
 	 * Kernel threads handle their own signals. Let the signal code
 	 * know it'll be handled, so that they don't get converted to
 	 * SIGKILL or just silently dropped.
 	 */
+	spin_lock_irq(&current->sighand->siglock);
 	current->sighand->action[(sig)-1].sa.sa_handler = (void __user *)2;
-	recalc_sigpending();
 	spin_unlock_irq(&current->sighand->siglock);
 }
 EXPORT_SYMBOL(allow_signal);