On Wednesday, June 26, 2013 09:12:51 PM Shuah Khan wrote: > On 06/25/2013 05:01 PM, Rafael J. Wysocki wrote: > > On Monday, June 24, 2013 05:25:18 PM Shuah Khan wrote: > >> pm_trace uses the system's Real Time Clock (RTC) to save the magic number. > >> Reason for this is that the RTC is the only reliably available piece of > >> hardware during resume operations where a value can be set that will > >> survive a reboot. > >> > >> Consequence is that after a resume (even if it is successful) your system > >> clock will have a value corresponding to the magic number instead of the > >> correct date/time! It is therefore advisable to use a program like ntp-date > >> or rdate to reset the correct date/time from an external time source when > >> using this trace option. > >> > >> There is no run-time message to warn users of the consequences of enabling > >> pm_trace. Adding a warning message to pm_trace_store() will serve as a > >> reminder to users to set the system date and time after resume. > >> > >> Signed-off-by: Shuah Khan <[email protected]> > >> --- > >> kernel/power/main.c | 2 ++ > >> 1 file changed, 2 insertions(+) > >> > >> diff --git a/kernel/power/main.c b/kernel/power/main.c > >> index d77663b..fd744d1 100644 > >> --- a/kernel/power/main.c > >> +++ b/kernel/power/main.c > >> @@ -528,6 +528,8 @@ pm_trace_store(struct kobject *kobj, struct > >> kobj_attribute *attr, > >> > >> if (sscanf(buf, "%d", &val) == 1) { > >> pm_trace_enabled = !!val; > >> + pr_warn("PM: Enabling pm_trace changes system date and time > >> after resume.\n"); > >> + pr_cont("PM: Remember to set correct time after resume\n"); > > > > You can do it like this: > > > > + pr_warn("PM: Enabling pm_trace changes system date and time after > > resume.\n" > > + "PM: Remember to set correct time after resume\n"); > > > > No need to use pr_cont(). :-) > > :) Yeah. > > > > > And I'd say "during" instead of "after" in the first sentence. > > > > I'd also say something like "Correct system time has to be restored > > manually after resume." > > instead of the second one. > > > > Will do. I think I should add a check and print this warning when > pm_trace is enabled and not when it is disabled. The way this patch is > done, it prints this warning for enable and disable. For both: > > echo 1 > pm_trace and echo 0 > pm_trace. > > Any thoughts?
Yeah, please only make it be printed when pm_trace is being enabled. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
