[Midnightbsd-cvs] src [8874] trunk/sys: mark ticks as volatile to avoid the compiler from caching in tight loops

[laffer1 at midnightbsd.org]

Revision: 8874
          http://svnweb.midnightbsd.org/src/?rev=8874
Author:   laffer1
Date:     2016-09-26 09:21:02 -0400 (Mon, 26 Sep 2016)
Log Message:
-----------
mark ticks as volatile to avoid the compiler from caching in tight loops

Modified Paths:
--------------
    trunk/sys/kern/kern_clock.c
    trunk/sys/sys/kernel.h

Modified: trunk/sys/kern/kern_clock.c
===================================================================
--- trunk/sys/kern/kern_clock.c	2016-09-26 13:20:01 UTC (rev 8873)
+++ trunk/sys/kern/kern_clock.c	2016-09-26 13:21:02 UTC (rev 8874)
@@ -381,7 +381,7 @@
 int	stathz;
 int	profhz;
 int	profprocs;
-int	ticks;
+volatile int	ticks;
 int	psratio;
 
 static DPCPU_DEFINE(int, pcputicks);	/* Per-CPU version of ticks. */
@@ -468,7 +468,7 @@
 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();

Modified: trunk/sys/sys/kernel.h
===================================================================
--- trunk/sys/sys/kernel.h	2016-09-26 13:20:01 UTC (rev 8873)
+++ trunk/sys/sys/kernel.h	2016-09-26 13:21:02 UTC (rev 8874)
@@ -63,7 +63,7 @@
 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 */