[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] [PATCH 2/4] time: add a notifier chain for when the system time is stepped

On 06/19/2013 10:13 AM, Konrad Rzeszutek Wilk wrote:
On Wed, Jun 19, 2013 at 09:52:06AM -0700, John Stultz wrote:
On 06/19/2013 08:25 AM, David Vrabel wrote:
From: David Vrabel <david.vrabel@xxxxxxxxxx>

The high resolution timer code gets notified of step changes to the
system time with clock_was_set() or clock_was_set_delayed() calls.  If
other parts of the kernel require similar notification there is no
clear place to hook into.

Add a clock_was_set atomic notifier chain
(clock_was_set_notifier_list) and call this in place of
clock_was_set().  If the timekeeping locks are held, the calls are
deferred to a new tasklet.

The hrtimer code adds a notifier block to this chain and uses it to
call (the now internal) clock_was_set().  Since the timekeeping code
does not call the chain from the timer irq clock_was_set_delayed() and
associated code can be removed.
So on my initial quick review, this *looks* pretty reasonable. I get
a little worried about interface abuse (ie: random drivers trying to
hook into clock_was_set_notifier_list), but we can move that into
timekeeper_internal.h or something similar to limit that.

The other issue here is we've been burned pretty badly in the past
with changes to clock_was_set(), as its key to keeping timers in
line with timekeeping.  So this will need a fair amount of testing
and run time before this gets merged, so 3.12 is what we'd be
targeting at the earliest (its getting a bit late for taking changes
for 3.11 anyway).
I think we have four weeks left? Or you think Linus is going to release
at the end of the month?

Well, I have to queue it, and then get Thomas to pull it from me, and that can take some time. And after -rc6 there's just not a lot of time for things to get testing in -next before being pushed to Linus. Its just a bit rushed for me.

If you want to try to push patch 1/4 in for 3.11 via the Xen tree,
I'll see about queuing the other three for hopefully 3.12.
OK, let me run them through the testing gauntleet to have the
warm fuzzy feeling.

Thanks.  I'll be running it through my test cases as well.


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.