From 13cc8b6ff0d8198102f60691c38c07151a693c7b Mon Sep 17 00:00:00 2001
From: Dominik Brodowski <linux@dominikbrodowski.net>
Date: Sun, 10 Aug 2008 21:34:54 +0200
Subject: [PATCH 2/2] acpi_pm.c: check for monotonicity
The current check for monotonicity is way too weak: Andreas Mohr reports
( http://lkml.org/lkml/2008/8/10/77 ) that on one of his test systems the
current check only triggers in 50% of all cases, leading to catastrophic timer
behaviour. To fix this issue, expand the check for monotonicity by doing ten
consecutive tests instead of one.
CC: John Stultz <johnstul@us.ibm.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
---
drivers/clocksource/acpi_pm.c | 42 ++++++++++++++++++++++++----------------
1 files changed, 25 insertions(+), 17 deletions(-)
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
index 2c00edd..f05c4fb 100644
--- a/drivers/clocksource/acpi_pm.c
+++ b/drivers/clocksource/acpi_pm.c
@@ -178,7 +178,7 @@ static int verify_pmtmr_rate(void)
static int __init init_acpi_pm_clocksource(void)
{
cycle_t value1, value2;
- unsigned int i;
+ unsigned int i, j, good = 0;
if (!pmtmr_ioport)
return -ENODEV;
@@ -187,24 +187,32 @@ static int __init init_acpi_pm_clocksource(void)
clocksource_acpi_pm.shift);
/* "verify" this timing source: */
- value1 = clocksource_acpi_pm.read();
- for (i = 0; i < 10000; i++) {
- value2 = clocksource_acpi_pm.read();
- if (value2 == value1)
- continue;
- if (value2 > value1)
- goto pm_good;
- if ((value2 < value1) && ((value2) < 0xFFF))
- goto pm_good;
- printk(KERN_INFO "PM-Timer had inconsistent results:"
- " 0x%#llx, 0x%#llx - aborting.\n", value1, value2);
- return -EINVAL;
+ for (j = 0; j < 10; j++) {
+ value1 = clocksource_acpi_pm.read();
+ for (i = 0; i < 10000; i++) {
+ value2 = clocksource_acpi_pm.read();
+ if (value2 == value1)
+ continue;
+ if (value2 > value1)
+ good++;
+ break;
+ if ((value2 < value1) && ((value2) < 0xFFF))
+ good++;
+ break;
+ printk(KERN_INFO "PM-Timer had inconsistent results:"
+ " 0x%#llx, 0x%#llx - aborting.\n",
+ value1, value2);
+ return -EINVAL;
+ }
+ udelay(300 * i);
+ }
+
+ if (good != 10) {
+ printk(KERN_INFO "PM-Timer had no reasonable result:"
+ " 0x%#llx - aborting.\n", value1);
+ return -ENODEV;
}
- printk(KERN_INFO "PM-Timer had no reasonable result:"
- " 0x%#llx - aborting.\n", value1);
- return -ENODEV;
-pm_good:
if (verify_pmtmr_rate() != 0)
return -ENODEV;
--
