Xavier Bestel <[EMAIL PROTECTED]> writes:
> Le dim 03/11/2002 � 18:47, Keith Packard a �crit :
> > Around 15 o'clock on Nov 3, Michel =?ISO-8859-1?Q?D=E4nzer?= wrote:
> >
> > > Oh, and are there any opinions about the signal to use, SIGALRM or
> > > something else?
> >
> > You'll have to make it settable -- SIGALRM is already used by the X server
> > for scheduling. Of course, we could eliminate that if I could get the
> > current time of day mapped into the X server address space :-)
>
> Just synchronizing from time to time and using TSC in the meantime isn't
> sufficient ?
Note that SMP issues make using the TSC safely really hard ..
TSC's aren't synchronized between processors on SMP systems,
and a process could get migrated at any time.
I think the Linux kernel people aren't yet sure if it's possible
to do a safe non-syscall high-resolution gettimeofday() for
these reasons.
Making the signal settable is definitely the right thing to do
in any case. What the /dev/rtc driver does is hook into SIGIO
so it can use fnctl (fd, F_SETSIG, ...); that setup could probably
be copied, though there may be better ways of doing it.
Regards,
Owen
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