Messages in this thread | | | Date | Mon, 09 Dec 2002 04:27:56 -0800 | From | george anzinger <> | Subject | Re: [PATCH 1/3] High-res-timers part 1 (core) take 20 |
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Arjan van de Ven wrote: > > On Sun, Dec 08, 2002 at 11:03:13PM -0800, george anzinger wrote: > > Arjan van de Ven wrote: > > > > > > On Sun, 2002-12-08 at 08:46, george anzinger wrote: > > > > > > > +/* > > > > + * Here is an SMP helping macro... > > > > + */ > > > > +#ifdef CONFIG_SMP > > > > +#define IF_SMP(a) a > > > > +#else > > > > +#define IF_SMP(a) > > > > +#endif > > > > > > ehmmmmm personally I would consider any need of this ugly and evil > > > > > > > + IF_SMP(if (old_base && (new_base != old_base)) > > > > + spin_unlock(&old_base->lock); > > > > + ) > > > > > > Like here..... SMP dependent ifdef's of spinlock usage... shudder > > > > > Well it does seem like a waste to do spinlock ordering code > > on a UP system... > > that's why spinlocks are effectively nops on UP. > What you say is true of just about every spinlock user, and no > they shouldn't all do some IF_SMP() thing; the spinlock itself should be > (and is) zero on UP
But with preemption, they really are not nops on UP... -- George Anzinger george@mvista.com High-res-timers: http://sourceforge.net/projects/high-res-timers/ Preemption patch: http://www.kernel.org/pub/linux/kernel/people/rml - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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