A couple more observation now that we've agreed on the approach.
On 01/08/2017 12:03, Paolo Bonzini wrote:
>
>>> Maybe what we want is some kind of "bool cycles_valid", and then
>>> read_clock_and_systime can return it:
>>>
>>>
>>> if (clock->read_clock_and_systime) {
>>> systime_snapshot->cycles_valid =
>>> clock->read_clock_and_systime(
>>> &now, &systime_snapshot->cycles);
Please pass the clocksource to the new function. However this:
> + clock = tk->tkr_mono.clock;
should then be READ_ONCE for the same reason mentioned in
tk_clock_read's comments. Then,
>>> } else {
>>> now = tk_clock_read(&tk->tkr_mono);
this can call clock->read(clock) directly, without going through
tk_clock_read.
Thanks,
Paolo
>>> systime_snapshot->cycles_valid = true;
>>> systime_snapshot->cycles = now;
>>> }
