Re: [PATCH] Fix posix-cpu-timer breakage caused by stalep->last_ran value

[Thomas Gleixner]

On Thu, 2007-02-22 at 08:46 +0100, Ingo Molnar wrote:
> * Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:
> 
> > The problem is that the p->last_ran value is not updated after a 
> > context switch. So a subsequent call to current_sched_time() 
> > calculates with a stale p->last_ran value, i.e. accounts the full 
> > time, which the task was scheduled away.
> > 
> > Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> 
> >  	sched_info_switch(prev, next);
> >  	if (likely(prev != next)) {
> > -		next->timestamp = now;
> > +		next->timestamp = next->last_ran = now;
> 
> ouch! nice catch. Also for v2.6.20.2 i think. 2.6.19 should be 
> unaffected.

Yes, was introduced in 2.6.20 and definitely should hit the stable tree.

	tglx


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