From 4ab6a219113197425ac112e35e1ec8062c69888e Mon Sep 17 00:00:00 2001 From: Dominik Brodowski Date: Fri, 5 Sep 2008 14:05:35 -0700 Subject: clocksource, 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. Signed-off-by: Dominik Brodowski Signed-off-by: Andrew Morton Signed-off-by: Ingo Molnar --- drivers/clocksource/acpi_pm.c | 46 +++++++++++++++++++++++++++---------------- 1 file changed, 29 insertions(+), 17 deletions(-) (limited to 'drivers') diff --git a/drivers/clocksource/acpi_pm.c b/drivers/clocksource/acpi_pm.c index 860d033bc74..4eee533f3f4 100644 --- a/drivers/clocksource/acpi_pm.c +++ b/drivers/clocksource/acpi_pm.c @@ -21,6 +21,7 @@ #include #include #include +#include #include /* @@ -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; -- cgit v1.2.3-70-g09d2