Re: [patch 01/18] x86, bts: fix race when bts tracer is removed

Ingo Molnar
2009-04-03T11:31:27Z

* Metzger, Markus T <markus.t.metzger@intel.com> wrote:

> >-----Original Message-----
> >From: Metzger, Markus T
> >Sent: Friday, April 03, 2009 8:20 AM
> >To: Ingo Molnar
>
>
> >>Also, raw use of jiffies_64 is buggy and racy. Why does this use
> >>jiffies to begin with - why not some finer grained time?
> >
> >What would be a good time to use?
>
> I found cpu_clock() declared in sched.h, which is based on TSC and
> seems to be used by the scheduler, as well. Would this be a good
> time to use?

i'd suggest trace_clock() [which maps to cpu_clock() internally], or
trace_clock_global().

See kernel/trace/trace_clock.c about the properties/tradeoffs. Since
this is a user-facing ABI, trace_clock_global() looks more
compelling, despite its global lock.

Ingo