On Wed, 26 Jul 2006 23:03:06 +0200 Arjan van de Ven <[email protected]> wrote: > I'm really starting to feel that the hotplug lock would have been better > of being a refcount (with a waitqueue for zero) than a lock. While > "refcount+waitqueue" sort of IS a lock, the semantics make more sense > imo... The mistake in the above paragraph is its use of the term "the hotplug lock". Think. We don't want to lock CPUs. We don't want to block plug/unplug events. What we _do_ want is for subsystems to be able to guarantee the stability of their per-cpu data and the coherency of that data with cpu_online_map and cpu_present_map. We should delete lock_cpu_hotplug() and start again. Perhaps we can do that post-2.6.18 if we can cobble the current stuff into some semi-working state. But I doubt if it's very important really - we have heaps of code in there which is already racy wrt hotplug and adding a little more isn't likely to hurt. I count 187 instances of for_each_online_cpu(), and most of them are racy. There's just no way we can fix all these with lock_cpu_hotplug(). It simply doesn't have a future. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] 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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