Re: [PATCH 2/2][RFC] kselftest: timers: Add adjtick test to validate adjtimex() tick adjustments

[Miroslav Lichvar]

On Tue, Sep 08, 2015 at 10:57:06PM -0700, John Stultz wrote:
> Recently an issue was reported that was difficult to detect except
> by tweaking the adjtimex tick value, and noticing how quickly the
> adjustment took to be made:
> 	https://lkml.org/lkml/2015/9/1/488
> 
> Thus this patch introduces a new test which manipulates the adjtimex
> tick value and validates the results are what we expect.

Great!

> +	ppm = ((long long)tickval * MILLION)/10000 - MILLION;

I think this needs to be based on sysconf(_SC_CLK_TCK) or similar,
since the user-space HZ is not 100 on all archs.

> +	for (tick = 9000; tick < 11000; tick += 250)
> +		if (check_tick_adj(tick)) {

This too.

> +	tx1.tick = 10000;
> +	adjtimex(&tx1);

And this too.

-- 
Miroslav Lichvar
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