include/linux/signal.h: mark expected switch fall-throughs

In preparation to enabling -Wimplicit-fallthrough, mark switch cases where
we are expecting to fall through.

Link: http://lkml.kernel.org/r/20181013114847.GA3160@embeddedor.com
Signed-off-by: Gustavo A. R. Silva <gustavo@embeddedor.com>
Acked-by: Kees Cook <keescook@chromium.org>
Reviewed-by: Michael Ellerman <mpe@ellerman.id.au>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/signal.h

@@ -129,9 +129,11 @@ static inline void name(sigset_t *r, const sigset_t *a, const sigset_t *b) \
 		b3 = b->sig[3]; b2 = b->sig[2];				\
 		r->sig[3] = op(a3, b3);					\
 		r->sig[2] = op(a2, b2);					\
+		/* fall through */					\
 	case 2:								\
 		a1 = a->sig[1]; b1 = b->sig[1];				\
 		r->sig[1] = op(a1, b1);					\
+		/* fall through */					\
 	case 1:								\
 		a0 = a->sig[0]; b0 = b->sig[0];				\
 		r->sig[0] = op(a0, b0);					\
@@ -161,7 +163,9 @@ static inline void name(sigset_t *set)					\
 	switch (_NSIG_WORDS) {						\
 	case 4:	set->sig[3] = op(set->sig[3]);				\
 		set->sig[2] = op(set->sig[2]);				\
+		/* fall through */					\
 	case 2:	set->sig[1] = op(set->sig[1]);				\
+		/* fall through */					\
 	case 1:	set->sig[0] = op(set->sig[0]);				\
 		    break;						\
 	default:							\
@@ -182,6 +186,7 @@ static inline void sigemptyset(sigset_t *set)
 		memset(set, 0, sizeof(sigset_t));
 		break;
 	case 2: set->sig[1] = 0;
+		/* fall through */
 	case 1:	set->sig[0] = 0;
 		break;
 	}
@@ -194,6 +199,7 @@ static inline void sigfillset(sigset_t *set)
 		memset(set, -1, sizeof(sigset_t));
 		break;
 	case 2: set->sig[1] = -1;
+		/* fall through */
 	case 1:	set->sig[0] = -1;
 		break;
 	}