Messages in this thread | | | Date | Fri, 7 May 2004 19:15:53 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: get_cmos_time() takes up to a second on boot |
| |
On Fri, 7 May 2004, Tim Bird wrote: > > What is the downside of disabling this > synchronization with the clock edge?
It might not matter any more, but if I remember correctly, the real problem was that we used to always write back the time to the CMOS clock too, and then booting a few times and consistently getting the time wrong the same way made the clock drift quite noticeably.
These days, I think we do the write-back only if we use an external clock (NTP), so we probably _could_ just remove the synchronization at read-time (removing it at write-time doesn't sound like a good idea).
Does anybody remember better?
> 1 second of variability is unnacceptable > when you're requirement is to boot in > .5 seconds. :)
Heh. And yes, it could be handled other ways (you could check the cmos time in the timer interrupt during boot, and correct it there rather than busy-waiting).
> Would it be bad to disable this synchronization > completely? How about just during boot?
I don't think we should necessarily disable the synchronization, but we could certainly make it optional for cases that don't care about it. We might even make the default be "don't care about the read synchronization".
Linus - 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/
| |