Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> Just like it seems to be the case for Steve (unless I misunderstood his
>>> reply), it is very useful for us being able to time-stamp events in RT
>>> context that need to be correlated with events stamped in non-RT
>>> (including non-Xenomai) parts or even on other systems: (offline) data
>>> fusion, logging, tracing. I even bet that this is currently the major
>>> use case for synchronized clocks, only a smaller part already has the
>>> need to synchronize timed activities on a common clock source. But there
>>> is huge potential in the second part once we can provide a stable
>>> infrastructure.
>> I already had such issues, and I did not solve them by modifying Xenomai
>> core.
>>> Even a "third clock" would have to be delivered for more archs than x86,
>>> no question. We would basically need a generic but slow syscall variant
>>> and per-arch syscall-less optimizations (where feasible).
>> So, you would add a syscall which would becomre useless when you have
>> implemented synchronized clocks properly? Yet another reason for
>> avoiding this solution.
> Could be "CLOCK_LINUX" - ie. no need for a new syscall.

I am Ok for this solution (and now that I think about it, I wonder if we
did not already have this discussion). Anyway, I would go for
CLOCK_HOST_REALTIME, in case someone wants to implement
CLOCK_HOST_MONOTONIC. The advantage is that we can return EINVAL in the
timer_create or clock_settime calls, to indicate clearly that using this
clock for timing services is verboten. And when/if the full
synchronization is implemented, the ID simply becomes a #define.


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