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Message-ID: <20080822222604.GA704@isilmar.linta.de>
Date: Sat, 23 Aug 2008 00:26:04 +0200
From: Dominik Brodowski <linux@...inikbrodowski.net>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: Andreas Mohr <andi@...as.de>, linux-kernel@...r.kernel.org,
linux-acpi@...r.kernel.org, johnstul@...ibm.com,
hirofumi@...l.parknet.co.jp, alan@...rguk.ukuu.org.uk,
arjan@...radead.org
Subject: [PATCH v2 2/2] acpi_pm.c: check for monotonicity
From: Dominik Brodowski <linux@...inikbrodowski.net>
Date: Fri, 22 Aug 2008 23:51:23 +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@...ibm.com>
CC: Thomas Gleixner <tglx@...utronix.de>
CC: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Dominik Brodowski <linux@...inikbrodowski.net>
---
drivers/clocksource/acpi_pm.c | 46 +++++++++++++++++++++++++---------------
1 files changed, 29 insertions(+), 17 deletions(-)
diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c
index 860d033..4eee533 100644
--- a/drivers/clocksource/acpi_pm.c
+++ b/drivers/clocksource/acpi_pm.c
@@ -21,6 +21,7 @@
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/pci.h>
+#include <linux/delay.h>
#include <asm/io.h>
/*
@@ -175,10 +176,13 @@ static int verify_pmtmr_rate(void)
#define verify_pmtmr_rate() (0)
#endif
+/* Number of monotonicity checks to perform during initialization */
+#define ACPI_PM_MONOTONICITY_CHECKS 10
+
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 +191,32 @@ 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 < ACPI_PM_MONOTONICITY_CHECKS; 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 != ACPI_PM_MONOTONICITY_CHECKS) {
+ printk(KERN_INFO "PM-Timer failed consistency check "
+ " (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;
--
1.5.2.5
--
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