job control: introduce JOBCTL_PENDING_MASK and task_clear_jobctl_pending()

This patch introduces JOBCTL_PENDING_MASK and replaces
task_clear_jobctl_stop_pending() with task_clear_jobctl_pending()
which takes an extra @mask argument.

JOBCTL_PENDING_MASK is currently equal to JOBCTL_STOP_PENDING but
future patches will add more bits.  recalc_sigpending_tsk() is updated
to use JOBCTL_PENDING_MASK instead.

task_clear_jobctl_pending() takes @mask which in subset of
JOBCTL_PENDING_MASK and clears the relevant jobctl bits.  If
JOBCTL_STOP_PENDING is set, other STOP bits are cleared together.  All
task_clear_jobctl_stop_pending() users are updated to call
task_clear_jobctl_pending() with JOBCTL_STOP_PENDING which is
functionally identical to task_clear_jobctl_stop_pending().

This patch doesn't cause any functional change.

Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
diff --git a/fs/exec.c b/fs/exec.c
index 8986bb0..4402105 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1772,7 +1772,7 @@
 
 	t = start;
 	do {
-		task_clear_jobctl_stop_pending(t);
+		task_clear_jobctl_pending(t, JOBCTL_STOP_PENDING);
 		if (t != current && t->mm) {
 			sigaddset(&t->pending.signal, SIGKILL);
 			signal_wake_up(t, 1);