Re: [patch 0/9] x86_64: reliable TSC-based gettimeofday

[john stultz <johnstul@us.ibm.com>]

On Thu, 2007-02-01 at 15:52 +0100, Jiri Bohac wrote:
> On Thu, Feb 01, 2007 at 12:20:59PM +0100, Andi Kleen wrote:
>>
> > The big strategic problem is how to marry your patchkit to John Stultz's
> > clocksources work which is also competing for merge. Any thoughts on that? 
> 
> I'll look into that next week. Sorry, I wanted to do that a long time
> ago, but I spent weeks (over a month) fighting a nasty livelock
> in the code. (Morale: think twice before using a spinlock inside
>                       a {do .. while (read_seqretry(..))} loop)

The first step here shouldn't be too difficult. Just create a _read
function that uses your code to return monotonic TSC cycles (instead of
nanoseconds w/ gettimeofday).  Then just create a clocksource structure
for it.

The harder part will be the vsyscall, as you will need extra per cpu
data in the vsyscall read. I had some test code for this situation
awhile back, so if you get the first part functioning correctly (just a
clocksource w/o a vread pointer), I'll gladly help you get the vsyscall
bits working.

thanks
-john