Re: [Lse-tech] Re: RFC: patch to allow lock-free traversal of lists with insertion

From: Rusty Russell (
Date: Sat Oct 13 2001 - 02:25:27 EST

In message <> you
> Yes. With maybe
> non_preempt()
> ..
> preempt()
> around it for the pre-emption patches.

Sure, if they want pre-emption on SMP. Of course, then they'll want
priority inheritence.

> However, you also need to make your free _free_ be aware of the count.
> Which means that the current RCU patch is really unusable for this. You
> need to have the "count" always in a generic place (put it with the hash),
> and your schedule-time free needs to do
> if (atomic_read(&count))
> skip_this_do_it_next_time

WTF? I'll spell it out for you again:

        static inline void foo_put(struct foo *foo)
                if (atomic_dec_and_test(foo->use))

Write side normal:


Write side RCU:

        rcu_call(foo_put, foo);
                /* ie. call foo_put(foo) "later". */

That's all. Really.

> Do that, and the RCU patches may start looking usable for the real world.

I know you're under strain, but think harder please.


Premature optmztion is rt of all evl. --DK
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