The estimate MHz routine is utterly busted.

At the least it should be binding to a CPU.
Also, the usleep doesn't make the CPU busy, so replace it with a loop
and wake up on an alarm after 3 seconds.

It's still wildly inaccurate. Not sure what to do yet, but this
is no more broken than it already was.

1 files changed, 35 insertions, 13 deletions

diff --git a/bench/MHz.c b/bench/MHz.c
index 0d429d7..87315a9 100644
--- a/bench/MHz.c
+++ b/bench/MHz.c
@@ -1,39 +1,50 @@
 /*
- *  This file is part of x86info.
  *  (C) 2001 Dave Jones.
  *
  *  Licensed under the terms of the GNU GPL License version 2.
- *
- * Estimate CPU MHz routine by Andrea Arcangeli <andrea@suse.de>
- * Small changes by David Sterba <sterd9am@ss1000.ms.mff.cuni.cz>
  */
 
 #include <stdio.h>
 #include <sys/time.h>
-#include <string.h>
 #include <unistd.h>
+#include <stdlib.h>
+
+#define _GNU_SOURCE
+#define __USE_GNU
+#include <sched.h>
+#include <string.h>
+#include <signal.h>
 
 #include "../x86info.h"
 
-unsigned long long int rdtsc(void)
+static unsigned long long int rdtsc(void)
 {
 	unsigned long long int x;
 	__asm__ volatile (".byte 0x0f, 0x31" : "=A" (x));
 	return x;
 }
 
+static volatile int nosignal = 0;
+
+static void sighandler(int sig __attribute__((unused)))
+{
+	nosignal = 1;
+}
+
 void estimate_MHz(struct cpudata *cpu)
 {
+	cpu_set_t set;
 	struct timezone tz;
 	struct timeval tvstart, tvstop;
 	unsigned long long int cycles[2]; /* gotta be 64 bit */
 	unsigned long microseconds; /* total time taken */
 	unsigned int eax, ebx, ecx, edx;
 	unsigned long freq = 1;
+	unsigned long i;
 
 	/* Make sure we have a TSC (and hence RDTSC) */
 	cpuid(cpu->number, 1, &eax, &ebx, &ecx, &edx);
-	if ((edx & (1<<4))==0) {
+	if ((edx & (1<<4)) == 0) {
 		printf("No TSC, MHz calculation cannot be performed.\n");
 		cpu->MHz = 0;
 		return;
@@ -41,15 +52,25 @@ void estimate_MHz(struct cpudata *cpu)
 
 	memset(&tz, 0, sizeof(tz));
 
-	/* get this function in cached memory */
-	gettimeofday(&tvstart, &tz);
+	if (sched_getaffinity(getpid(), sizeof(set), &set) == 0) {
+		CPU_ZERO(&set);
+		CPU_SET(cpu->number, &set);
+		sched_setaffinity(getpid(), sizeof(set), &set);
+	}
+
+	if (signal(SIGALRM, sighandler) == SIG_ERR) {
+		printf("Some kind of signal failure.\n");
+		return;
+	}
+
 	cycles[0] = rdtsc();
 	gettimeofday(&tvstart, &tz);
 
-	/* we don't trust that this is any specific length of time */
-	usleep(250000);
+	alarm(3);
+	while (!nosignal) {
+		i = i * rand();
+	}
 
-	gettimeofday(&tvstop, &tz);
 	cycles[1] = rdtsc();
 	gettimeofday(&tvstop, &tz);
 
@@ -62,5 +83,6 @@ void estimate_MHz(struct cpudata *cpu)
 		cpu->MHz = ((cpu->MHz / 50) * 50) + 50;
 	else
 		cpu->MHz = ((cpu->MHz / 50) * 50);
-}
 
+	nosignal = 0;
+}