Hi,
On Mon, 13 Feb 2006, Thomas Gleixner wrote:
> This adds an artificial offset to the expiry time, for what reason? The
> expiry code makes sure that timers can not expire early. See:
>
> timer = rb_entry(node, struct hrtimer, node);
> if (now.tv64 <= timer->expires.tv64)
> break;
>
> in kernel/hrtimers.c:run_hrtimer_queue(), where now is already tick
> aligned.
>
> Please provide a testcase (or detailed use-case) which proves that this
> is necessary.
Let's assume a get_time() which simply returns xtime and so has a
resolution of around TICK_NSEC. This means the real time when one calls
get_time() is somewhere between xtime and xtime+TICK_NSEC. Assuming the
real time is xtime+TICK_NSEC-1, get_time() will return xtime and a
relative timer with TICK_NSEC-1 will expire immediately.
The old code did this correctly. For most hardware this is not a real
issue, as the delivery time is larger than the clock resolution, but
unless you can guarantee it's not an issue on _any_ supported hardware,
this fix is needed. As I already said this can be better fixed as soon as
we have a better clock abstraction, until then this is only restores the
old behaviour.
bye, Roman
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
