Messages in this thread | | | Date | Mon, 19 Dec 2005 12:54:31 -0800 | From | George Anzinger <> | Subject | Re: [patch 00/21] hrtimer - High-resolution timer subsystem |
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Roman Zippel wrote: > Hi, > > On Wed, 14 Dec 2005, George Anzinger wrote: > > >>>>IMHO then, the result should have the same property, i.e. ABS_TIME. Sort >>>>of >>>>like adding an offset to a relative address. The result is still relative. >>> >>> >>>If the result is relative, why should have a clock set any effect? >>>IMO the spec makes it quite clear that initial timer and the periodic timer >>>are two different types of the timer. The initial timer only specifies how >>>the periodic timer is started and the periodic timer itself is a "relative >>>time service". >>> >> >>Well, I guess we will have to agree to disagree. > > > That's easy for you to say. :) > You don't think the current behaviour is wrong. > > On of the issues I see with using your assumption is that moving the timer to an absolute clock after the initial expiry _may_ lead to additional qauntization errors, depending on how aligned the two clocks are.
>> That which the interval is >>added to is an absolute time, so I, and others, take the result as absolute. >>At this point there really is no "conversion" to an absolute timer. Once the >>timer initial time is absolute, everything derived from it, i.e. all intervals >>added to it, must be absolute. > > > With this argumentation, any relative timer could be treated this way, you > have to base a relative timer on something. > While searching for more information I found the NetBSD code and they > do exactly this, they just convert everything to absolute values and clock > set affects all timers equally. Is this now more correct? > I would guess, then, that either the non-absolute or the absolute timer behaves badly in the face of clock setting. Could you provide a pointer to the NetBSD code so I can have a look too? > >>For what its worth, I do think that the standards folks could have done a bit >>better here. I, for example, would have liked to have seen a discussion about >>what to do with overrun in the face of clock setting. > > > Maybe they thought it wouldn't be necessary :), because a periodic is a > relative timer and thus not affected...
Well, then they could have said that :) Might have prevented a lot of lkml bandwidth usage as well as several days of my time trying to do something other than what they might say is the right thing.
-- George Anzinger george@mvista.com HRT (High-res-timers): http://sourceforge.net/projects/high-res-timers/ - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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