On 05/17/2013 11:24 AM, Zoran Markovic wrote:
Since commit <31ade30692dc9680bfc95700d794818fa3f754ac>, timekeeping_init() checks for presence of persistent clock by attempting to read a non-zero time value from real-time clock. This is an issue on platforms where persistent_clock (instead of a RTC) is implemented as a free-running counter starting from zero on each boot and running during suspend. Examples are some ARM platforms (e.g. PandaBoard). An attempt to read such a clock during timekeeping_init() may return zero value and falsely declare persistent clock as missing. Additionally, in the above case suspend times may be accounted twice (once from timekeeping_resume() and once from rtc_resume()), resulting in a gradual drift of system time. This patch does a run-time correction of the issue by doing the same check during timekeeping_suspend(). A better long-term solution would have to return error when trying to read non-existing clock and zero when trying to read an uninitialized clock, but that would require changing all persistent_clock implementations. This patch addresses the immediate breakage, for now. Cc: John Stultz <john.stultz@xxxxxxxxxx> Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx> Cc: Feng Tang <feng.tang@xxxxxxxxx> Cc: stable@xxxxxxxxxxxxxxx Signed-off-by: Zoran Markovic <zoran.markovic@xxxxxxxxxx>
Thanks for finding and sending this out! I'll queue this for 3.10. thanks again -john -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html