> So the basic issue I mentioned is that:
>
>
> /*
> * ,------------------------[1:n]---------------------.
> * V V
> * perf_event_context <-[1:n]-> perf_event_pmu_context <--- perf_event
> * ^ ^ | |
> * `--------[1:n]---------' `-[n:1]-> pmu <-[1:n]-'
> *
> *
> * XXX destroy epc when empty
> * refcount, !rcu
> *
> * XXX epc locking
> *
> * event->pmu_ctx ctx->mutex && inactive
> * ctx->pmu_ctx_list ctx->mutex && ctx->lock
> *
> */
> struct perf_event_pmu_context {
> ...
> atomic_t refcount; /* event <-> epc */
> ...
> }
>
> But that then also suggests that:
>
> struct perf_event_context {
> ...
> refcount_t refcount;
> ...
> }
>
> should be: ctx <-> epc, and that is not so, the ctx::refcount still
> counts the number of events.
>
> Now this might not be bad, but it is confusing.
I don't have strong opinion, but we store events in ctx, not in pmu_ctx.
So, I think it makes sense to keep refcount as ctx <-> event?
[...]
> +void perf_pmu_migrate_context(struct pmu *pmu, int src_cpu, int dst_cpu)
> +{
> + struct perf_event_context *src_ctx, *dst_ctx;
> + LIST_HEAD(events);
> +
> + src_ctx = &per_cpu_ptr(&cpu_context, src_cpu)->ctx;
> + dst_ctx = &per_cpu_ptr(&cpu_context, dst_cpu)->ctx;
> +
> + /*
> + * See perf_event_ctx_lock() for comments on the details
> + * of swizzling perf_event::ctx.
> + */
> + mutex_lock_double(&src_ctx->mutex, &dst_ctx->mutex);
> +
> + __perf_pmu_remove(src_ctx, src_cpu, pmu, &src_src->pinned_groups, &events);
> + __perf_pmu_remove(src_ctx, src_cpu, pmu, &src_src->flexible_groups, &events);
Rbtrees does not contain sibling events. Shouldn't we continue using
event_list here?
Thanks,
Ravi
