Re: [RFC][PATCH] new timeofday core subsystem (v. A3)

From: George Anzinger
Date: Mon Mar 14 2005 - 18:44:52 EST

john stultz wrote:
On Sat, 2005-03-12 at 16:49 -0800, Matt Mackall wrote:


+ /* finally, update legacy time values */
+ write_seqlock_irqsave(&xtime_lock, x_flags);
+ xtime = ns2timespec(system_time + wall_time_offset);
+ wall_to_monotonic = ns2timespec(wall_time_offset);
+ wall_to_monotonic.tv_sec = -wall_to_monotonic.tv_sec;
+ wall_to_monotonic.tv_nsec = -wall_to_monotonic.tv_nsec;
+ /* XXX - should jiffies be updated here? */

Excellent question.

Indeed. Currently jiffies is used as both a interrupt counter and a
time unit, and I'm trying make it just the former. If I emulate it then
it stops functioning as a interrupt counter, and if I don't then I'll
probably break assumptions about jiffies being a time unit. So I'm not
sure which is the easiest path to go until all the users of jiffies are
audited for intent.

Really? Who counts interrupts??? The timer code treats jiffies as a unit of time. You will need to rewrite that to make it otherwise. But then you have another problem. To correctly function, times need to expire on time (hay how bout that) not some time later. To do this we need an interrupt source. To this point in time, the jiffies interrupt has been the indication that one or more timer may have expired. While we don't need to "count" the interrupts, we DO need them to expire the timers AND they need to be on time.

George Anzinger george@xxxxxxxxxx

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at