[RFC] Posix compliant behavior of CLOCK_PROCESS/THREAD_CPUTIME_ID

[Roland McGrath]

Sorry I haven't replied sooner.  I don't think the facility offered by your
patch is enough by itself to be worth doing.  That information about a
process is already available to itself via getrusage/times, though those
don't offer a per-thread sample.  

I have been working on an alternate patch that implements more complete CPU
clock functionality.  This includes access to other threads' and process'
times, potentially finer-grained information (based on sched_clock), and
timers.  I will post this code when it's ready, hopefully soon.

As to supporting clock_settime, I think that is just plain not desireable.
I am not aware of any actual demand for it, and POSIX certainly does not
require that it be permitted.  It's certainly undesireable to let a process
reset its actual totals as reported by getrusage, process accounting, etc.;
I gather your later revisions have at least avoided that pitfall.  But I
don't really see the utility in letting applications use clock_settime on
their CPU clocks either.  They can just save the starting value at the time
they would use clock_settime to reset it to zero, and compute the delta later.



Thanks,
Roland