From a8df530ddc1c97a009f26d18219c6e84d976c2aa Mon Sep 17 00:00:00 2001
From: John Baldwin <jhb@FreeBSD.org>
Date: Mon, 28 Jan 2013 19:38:13 +0000
Subject: [PATCH] Mark 'ticks', 'time_second', and 'time_uptime' as volatile to
 prevent the compiler from caching their values in tight loops.

Reviewed by:	bde
MFC after:	1 week
---
 sys/dev/usb/net/if_cdce.c | 4 +++-
 sys/kern/kern_clock.c     | 4 ++--
 sys/kern/kern_tc.c        | 4 ++--
 sys/pci/ncr.c             | 2 +-
 sys/sys/kernel.h          | 2 +-
 sys/sys/time.h            | 4 ++--
 6 files changed, 11 insertions(+), 9 deletions(-)

diff --git a/sys/dev/usb/net/if_cdce.c b/sys/dev/usb/net/if_cdce.c
index 6e0ce97c36f8..e214fe21c4b7 100644
--- a/sys/dev/usb/net/if_cdce.c
+++ b/sys/dev/usb/net/if_cdce.c
@@ -500,6 +500,7 @@ cdce_attach(device_t dev)
 	const struct usb_interface_descriptor *id;
 	const struct usb_cdc_ethernet_descriptor *ued;
 	const struct usb_config *pcfg;
+	uint32_t seed;
 	int error;
 	uint8_t i;
 	uint8_t data_iface_no;
@@ -612,8 +613,9 @@ cdce_attach(device_t dev)
 		/* fake MAC address */
 
 		device_printf(dev, "faking MAC address\n");
+		seed = ticks;
 		sc->sc_ue.ue_eaddr[0] = 0x2a;
-		memcpy(&sc->sc_ue.ue_eaddr[1], &ticks, sizeof(uint32_t));
+		memcpy(&sc->sc_ue.ue_eaddr[1], &seed, sizeof(uint32_t));
 		sc->sc_ue.ue_eaddr[5] = device_get_unit(dev);
 
 	} else {
diff --git a/sys/kern/kern_clock.c b/sys/kern/kern_clock.c
index 5e10200a49ad..9d62c58524ae 100644
--- a/sys/kern/kern_clock.c
+++ b/sys/kern/kern_clock.c
@@ -382,7 +382,7 @@ static void watchdog_config(void *, u_int, int *);
 int	stathz;
 int	profhz;
 int	profprocs;
-int	ticks;
+volatile int	ticks;
 int	psratio;
 
 static DPCPU_DEFINE(int, pcputicks);	/* Per-CPU version of ticks. */
@@ -469,7 +469,7 @@ void
 hardclock(int usermode, uintfptr_t pc)
 {
 
-	atomic_add_int((volatile int *)&ticks, 1);
+	atomic_add_int(&ticks, 1);
 	hardclock_cpu(usermode);
 	tc_ticktock(1);
 	cpu_tick_calibration();
diff --git a/sys/kern/kern_tc.c b/sys/kern/kern_tc.c
index a08b218cd19c..2ffa2f9426fd 100644
--- a/sys/kern/kern_tc.c
+++ b/sys/kern/kern_tc.c
@@ -103,8 +103,8 @@ static struct timecounter *timecounters = &dummy_timecounter;
 
 int tc_min_ticktock_freq = 1;
 
-time_t time_second = 1;
-time_t time_uptime = 1;
+volatile time_t time_second = 1;
+volatile time_t time_uptime = 1;
 
 struct bintime boottimebin;
 struct timeval boottime;
diff --git a/sys/pci/ncr.c b/sys/pci/ncr.c
index 793ae80154db..ead7d4389c02 100644
--- a/sys/pci/ncr.c
+++ b/sys/pci/ncr.c
@@ -1386,7 +1386,7 @@ static char *ncr_name (ncb_p np)
  * Kernel variables referenced in the scripts.
  * THESE MUST ALL BE ALIGNED TO A 4-BYTE BOUNDARY.
  */
-static void *script_kvars[] =
+static volatile void *script_kvars[] =
 	{ &time_second, &ticks, &ncr_cache };
 
 static	struct script script0 = {
diff --git a/sys/sys/kernel.h b/sys/sys/kernel.h
index 441bcb3d628c..c54677a8d810 100644
--- a/sys/sys/kernel.h
+++ b/sys/sys/kernel.h
@@ -63,7 +63,7 @@ extern int psratio;			/* ratio: prof / stat */
 extern int stathz;			/* statistics clock's frequency */
 extern int profhz;			/* profiling clock's frequency */
 extern int profprocs;			/* number of process's profiling */
-extern int ticks;
+extern volatile int ticks;
 
 #endif /* _KERNEL */
 
diff --git a/sys/sys/time.h b/sys/sys/time.h
index 12d43cf7c61e..80878c0e9f8e 100644
--- a/sys/sys/time.h
+++ b/sys/sys/time.h
@@ -287,8 +287,8 @@ struct clockinfo {
 void	inittodr(time_t base);
 void	resettodr(void);
 
-extern time_t	time_second;
-extern time_t	time_uptime;
+extern volatile time_t	time_second;
+extern volatile time_t	time_uptime;
 extern struct bintime boottimebin;
 extern struct timeval boottime;