Re: [PATCH v2 1/4] time: rtc-lib: Add rtc_show_time(const char *prefix_msg)

[Mark Salyzyn]

On 07/19/2017 05:03 AM, Prarit Bhargava wrote:
> On 07/19/2017 03:23 AM, Thomas Gleixner wrote:
> > On Tue, 18 Jul 2017, Mark Salyzyn wrote:
> > > On 07/18/2017 03:35 PM, Thomas Gleixner wrote:
> > > > There was some discussion about making the clock source for dmesg time
> > > > stamps selectable, so you can use MONOTONIC, REALTIME, BOOTTIME. The
> > > > patches looked sensible, but there was some showstopper vs. the user space
> > > > dmesg utility. See:
> > > The timestamps are useful for the 'second' purpose of these patches when
> > > dmesg time is BOOTTIME or MONOTONIC, and can be turned off if REALTIME
> > > is selected. Having rtc_show_time a single point for switching this no doubt
> > > helps,
> > > not hinders, that dmesg issue.
> > >
> > > The inflection points would still serve a purpose, still need
> > > suspend/resume/hibernate/restore. The reboot messages are _only_ useful to
> > > us with their timestamps, as I checked and the only tools that use those are
> > > for log synchronization. We may be able to do away with them on REALTIME
> > > dmesg'ing; but the standardization of the message as a marker would have a
> > > legacy purpose (!)
> > >
> > > NB: We have a similar configuration for the user space logger, which can be
> > > configured to report in MONOTONIC time. We have yet to have a vendor
> > > use the feature, opting for REALTIME logging for user space activities.
> > > Our klogd (which runs at background priority and is batched) manages a
> > > histogram relationship between MONOTONIC and REALTIME helped by these
> > > prints and incorporates the REALTIME dmesg logs merged into our user
> > > space logging database.
> > There is another option to remedy this and the dmesg tooling issues:
> >
> > Instead of switching the time stamps in dmesg to a different clock we might
> > as well have an optional secondary timestamp. So instead of:
> >
> >   [  341.590930] wlan0: associated
> >
> > you would get:
> >
> >   [  341.590930] [ sec.usec] wlan0: associated
> >
> > where the second time stamp would be CLOCK_REALTIME/BOOTTIME.
> >
> > That should also solve Prarits problem, hmm?
> It would but I would prefer a single time stamp be printed than two.  I think
> two timestamps is adding confusion to the output from a end-users point of view.

Agreed, and so many tools will be in pain (toybox, busybox, for 
instance). Not that I disagree, but API changes should always get an 
environmental assessment ...

> Mark, why don't we get together and fixup my original patchset to make sure it
> meets your needs?  It will fix both of our issues albeit not necessarily in the
> text format you want it.
I am currently retesting with the rtc format patch rolled out 
separately, could probably roll into your set.

-- Mark