linux-kernel - Re: [PATCH 1/2] hrtimers: extend hrtimer base code to handle more then 2 clockids

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Date:	Tue, 01 Feb 2011 10:37:28 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	Jamie Lokier <jamie@...reable.org>,
	Alexander Shishkin <virtuoso@...nd.org>,
	Arve Hjønnevåg <arve@...roid.com>
Subject: Re: [PATCH 1/2] hrtimers: extend hrtimer base code to handle more
 then 2 clockids

On Tue, 2011-02-01 at 15:10 +0100, Thomas Gleixner wrote:
> On Mon, 31 Jan 2011, John Stultz wrote:
> > @@ -53,11 +53,10 @@
> >  /*
> >   * The timer bases:
> >   *
> > - * Note: If we want to add new timer bases, we have to skip the two
> > - * clock ids captured by the cpu-timers. We do this by holding empty
> > - * entries rather than doing math adjustment of the clock ids.
> > - * This ensures that we capture erroneous accesses to these clock ids
> > - * rather than moving them into the range of valid clock id's.
> > + * There are more clockids then hrtimer bases. Thus, we index
> 
> s/then/than/

Thenks! ;)

> > + * into the timer bases by the hrtimer_base_type enum. When trying
> > + * to reach a base using a clockid, hrtimer_clockid_to_base()
> > + * is used to convert from clockid to the proper hrtimer_base_type.
> >   */
> >  DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
> >  {
> > @@ -77,6 +76,24 @@ DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
> >  	}
> >  };
> >  
> > +static int hrtimer_clock_to_base_table[MAX_CLOCKS];
> > +
> > +static inline int hrtimer_clockid_to_base(clockid_t clock_id)
> > +{
> > +	int ret = hrtimer_clock_to_base_table[clock_id];
> > +
> > +	if(ret == -1) {
> > +		WARN_ON(1);
> > +		/* We just hit an invalid clock base,
> > +		 * but returning -1 isn't safe, so
> > +		 * return the _REALTIME base
> > +		 */
> 
>   How can this happen ?

It can't right now. I'm just worried someone will try to put a clockid
that doesn't have an hrtimer base into that function sometime in the
future. We can wrap it in a debug config maybe?

thanks
-john


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