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scx: Prepare for BPF DSQ iterator #182
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The function takes @Mask but ignores it and uses hard-coded __SCX_KF_RQ_LOCKED instead. Fix it. The only user was calling with __SCX_KF_RQ_LOCKED, so this doesn't cause any behavior changes.
It's currently marked ops-only but can actually be called from any context. Let's make it safe.
None of the functions in scx_kfunc_set_ops_only set are ops-only. scx_bpf_select_cpu_dfl() is select_cpu-only and the rest can be called from anywhere. Remove the set and move the kfuncs to scx_kfunc_set_any and the new scx_kfunc_set_select_cpu. No functional changes intended.
We'll use the list_head for both fifo and priq. Let's rename it to list. No functional changes intended.
priq will updated so that the tasks are added to the list in vtime order too. Thus, caching the first node won't be necessary. Let's switch to uncached variant.
When a DSQ is used as a PRIQ, tasks were only kept on dsq->priq. This requires all other paths to check both dsq->priq and dsq->list. A task's scx.dsq_node.list is available when the task is on a PRIQ DSQ anyway, let's always put tasks on dsq->list whether it's used as a PRIQ or FIFO by inserting into dsq->list in vtime order on PRIQs. This means that dsq->list is always in dispatch order whether the DSQ is FIFO or PRIQ and the only paths that need to worry about the DSQ type are dispatch_enqueue() and task_unlink_from_dsq().
- Relocate scx_task_iter definition so that it's together with iter functions. - Add find_user_dsq() instead of open-coding rhashtable_lookup_fast(). No functional changes.
and give p->scx.dsq_node's type the name of scx_dsq_node. This will be used to implement DSQ iterator. This wastes 8 bytes on 64bit. Oh well.
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SCX_KFusages.dsq->listin dispatch order whether the DSQ is FIFO or PRIQ.