kernel: use gettime(9)/getuptime(9) in lieu of time_second(9)/time_uptime(9)

time_second(9) and time_uptime(9) are widely used in the kernel to
quickly get the system UTC or system uptime as a time_t.  However,
time_t is 64-bit everywhere, so it is not generally safe to use them
on 32-bit platforms: you have a split-read problem if your hardware
cannot perform atomic 64-bit reads.

This patch replaces time_second(9) with gettime(9), a safer successor
interface, throughout the kernel.  Similarly, time_uptime(9) is replaced
with getuptime(9).

There is a performance cost on 32-bit platforms in exchange for
eliminating the split-read problem: instead of two register reads you
now have a lockless read loop to pull the values from the timehands.
This is really not *too* bad in the grand scheme of things, but
compared to what we were doing before it is several times slower.

There is no performance cost on 64-bit (__LP64__) platforms.

With input from visa@, dlg@, and tedu@.

Several bugs squashed by visa@.

ok kettenis@

1 files changed, 6 insertions, 6 deletions

diff --git a/sys/net/if_bpe.c b/sys/net/if_bpe.c
index b9a88be8efa..13224499bb1 100644
--- a/sys/net/if_bpe.c
+++ b/sys/net/if_bpe.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_bpe.c,v 1.10 2019/11/07 07:36:31 dlg Exp $ */
+/*	$OpenBSD: if_bpe.c,v 1.11 2020/06/24 22:03:43 cheloha Exp $ */
 /*
  * Copyright (c) 2018 David Gwynne <dlg@openbsd.org>
  *
@@ -230,7 +230,7 @@ bpe_entry_valid(struct bpe_softc *sc, const struct bpe_entry *be)
 	if (be->be_type == BPE_ENTRY_STATIC)
 		return (1);
 
-	diff = time_uptime - be->be_age;
+	diff = getuptime() - be->be_age;
 	if (diff < sc->sc_bridge_tmo)
 		return (1);
 
@@ -343,7 +343,7 @@ bpe_bridge_age(void *arg)
 		if (be->be_type != BPE_ENTRY_DYNAMIC)
 			continue;
 
-		diff = time_uptime - be->be_age;
+		diff = getuptime() - be->be_age;
 		if (diff < sc->sc_bridge_tmo)
 			continue;
 
@@ -402,7 +402,7 @@ bpe_rtfind(struct bpe_softc *sc, struct ifbaconf *baconf)
 
 		switch (be->be_type) {
 		case BPE_ENTRY_DYNAMIC:
-			age = time_uptime - be->be_age;
+			age = getuptime() - be->be_age;
 			bareq.ifba_age = MIN(age, 0xff);
 			bareq.ifba_flags = IFBAF_DYNAMIC;
 			break;
@@ -833,7 +833,7 @@ bpe_input_map(struct bpe_softc *sc, const uint8_t *ba, const uint8_t *ca)
 	if (be == NULL)
 		new = 1;
 	else {
-		be->be_age = time_uptime; /* only a little bit racy */
+		be->be_age = getuptime(); /* only a little bit racy */
 
 		if (be->be_type != BPE_ENTRY_DYNAMIC ||
 		    ETHER_IS_EQ(ba, &be->be_b_da))
@@ -857,7 +857,7 @@ bpe_input_map(struct bpe_softc *sc, const uint8_t *ba, const uint8_t *ca)
 		memcpy(&be->be_b_da, ba, sizeof(be->be_b_da));
 		be->be_type = BPE_ENTRY_DYNAMIC;
 		refcnt_init(&be->be_refs);
-		be->be_age = time_uptime;
+		be->be_age = getuptime();
 
 		rw_enter_write(&sc->sc_bridge_lock);
 		num = sc->sc_bridge_num;