From: Ingo Molnar
> Sent: 30 December 2023 20:38
>
> * David Laight <David.Laight@xxxxxxxxxx> wrote:
>
> > bool osq_lock(struct optimistic_spin_queue *lock)
> > {
> > - struct optimistic_spin_node *node = this_cpu_ptr(&osq_node);
> > + struct optimistic_spin_node *node = raw_cpu_read(osq_node.self);
> > struct optimistic_spin_node *prev, *next;
> > int old;
> >
> > - if (unlikely(node->cpu == OSQ_UNLOCKED_VAL))
> > - node->cpu = encode_cpu(smp_processor_id());
> > + if (unlikely(!node)) {
> > + int cpu = encode_cpu(smp_processor_id());
> > + node = decode_cpu(cpu);
> > + node->self = node;
> > + node->cpu = cpu;
>
> This whole initialization sequence is suboptimal and needs to be
> cleaned up first: the node->cpu field is constant once initialized, so
> it should be initialized from appropriate init methods, not runtime in
> osq_lock(), right?
I thought that as well, but there would need to be a list of 'init'
functions for the per-cpu data. I didn't spot one.
David
-
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