On 11/15/2012 02:56 AM, Julius Werner wrote: > Many cpuidle drivers measure their time spent in an idle state by > reading the wallclock time before and after idling and calculating the > difference. This leads to erroneous results when the wallclock time gets > updated by another processor in the meantime, adding that clock > adjustment to the idle state's time counter. > > If the clock adjustment was negative, the result is even worse due to an > erroneous cast from int to unsigned long long of the last_residency > variable. The negative 32 bit integer will zero-extend and result in a > forward time jump of roughly four billion milliseconds or 1.3 hours on > the idle state residency counter. > > This patch changes all affected cpuidle drivers to either use the > monotonic clock for their measurements or make use of the generic time > measurement wrapper in cpuidle.c, which was already working correctly. > Some superfluous CLIs/STIs in the ACPI code are removed (interrupts > should always already be disabled before entering the idle function, and > not get reenabled until the generic wrapper has performed its second > measurement). It also removes the erroneous cast, making sure that > negative residency values are applied correctly even though they should > not appear anymore. > > Signed-off-by: Julius Werner <jwerner@xxxxxxxxxxxx> Tested on a Core 2 Duo (processor_idle driver). Tested-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx> -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
