From: Tejun Heo Date: Sat, 7 Mar 2026 15:29:50 +0000 (-1000) Subject: sched_ext: Add per-CPU data to DSQs X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=30b0515342db48ac9ffd9999648de0f7ca1d6a87;p=thirdparty%2Fkernel%2Flinux.git sched_ext: Add per-CPU data to DSQs Add per-CPU data structure to dispatch queues. Each DSQ now has a percpu scx_dsq_pcpu which contains a back-pointer to the DSQ. This will be used by future changes to implement per-CPU reenqueue tracking for user DSQs. init_dsq() now allocates the percpu data and can fail, so it returns an error code. All callers are updated to handle failures. exit_dsq() is added to free the percpu data and is called from all DSQ cleanup paths. In scx_bpf_create_dsq(), init_dsq() is called before rcu_read_lock() since alloc_percpu() requires GFP_KERNEL context, and dsq->sched is set afterwards. v2: Fix err_free_pcpu to only exit_dsq() initialized bypass DSQs (Andrea Righi). Signed-off-by: Tejun Heo Reviewed-by: Andrea Righi --- diff --git a/include/linux/sched/ext.h b/include/linux/sched/ext.h index f354d7d343069..98cc1f41b91e3 100644 --- a/include/linux/sched/ext.h +++ b/include/linux/sched/ext.h @@ -62,6 +62,10 @@ enum scx_dsq_id_flags { SCX_DSQ_LOCAL_CPU_MASK = 0xffffffffLLU, }; +struct scx_dsq_pcpu { + struct scx_dispatch_q *dsq; +}; + /* * A dispatch queue (DSQ) can be either a FIFO or p->scx.dsq_vtime ordered * queue. A built-in DSQ is always a FIFO. The built-in local DSQs are used to @@ -79,6 +83,7 @@ struct scx_dispatch_q { struct rhash_head hash_node; struct llist_node free_node; struct scx_sched *sched; + struct scx_dsq_pcpu __percpu *pcpu; struct rcu_head rcu; }; diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index d8ea12ddc2069..aea09eb36873e 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -4020,15 +4020,42 @@ DEFINE_SCHED_CLASS(ext) = { #endif }; -static void init_dsq(struct scx_dispatch_q *dsq, u64 dsq_id, - struct scx_sched *sch) +static s32 init_dsq(struct scx_dispatch_q *dsq, u64 dsq_id, + struct scx_sched *sch) { + s32 cpu; + memset(dsq, 0, sizeof(*dsq)); raw_spin_lock_init(&dsq->lock); INIT_LIST_HEAD(&dsq->list); dsq->id = dsq_id; dsq->sched = sch; + + dsq->pcpu = alloc_percpu(struct scx_dsq_pcpu); + if (!dsq->pcpu) + return -ENOMEM; + + for_each_possible_cpu(cpu) { + struct scx_dsq_pcpu *pcpu = per_cpu_ptr(dsq->pcpu, cpu); + + pcpu->dsq = dsq; + } + + return 0; +} + +static void exit_dsq(struct scx_dispatch_q *dsq) +{ + free_percpu(dsq->pcpu); +} + +static void free_dsq_rcufn(struct rcu_head *rcu) +{ + struct scx_dispatch_q *dsq = container_of(rcu, struct scx_dispatch_q, rcu); + + exit_dsq(dsq); + kfree(dsq); } static void free_dsq_irq_workfn(struct irq_work *irq_work) @@ -4037,7 +4064,7 @@ static void free_dsq_irq_workfn(struct irq_work *irq_work) struct scx_dispatch_q *dsq, *tmp_dsq; llist_for_each_entry_safe(dsq, tmp_dsq, to_free, free_node) - kfree_rcu(dsq, rcu); + call_rcu(&dsq->rcu, free_dsq_rcufn); } static DEFINE_IRQ_WORK(free_dsq_irq_work, free_dsq_irq_workfn); @@ -4234,15 +4261,17 @@ static void scx_sched_free_rcu_work(struct work_struct *work) cgroup_put(sch_cgroup(sch)); #endif /* CONFIG_EXT_SUB_SCHED */ - /* - * $sch would have entered bypass mode before the RCU grace period. As - * that blocks new deferrals, all deferred_reenq_local_node's must be - * off-list by now. - */ for_each_possible_cpu(cpu) { struct scx_sched_pcpu *pcpu = per_cpu_ptr(sch->pcpu, cpu); + /* + * $sch would have entered bypass mode before the RCU grace + * period. As that blocks new deferrals, all + * deferred_reenq_local_node's must be off-list by now. + */ WARN_ON_ONCE(!list_empty(&pcpu->deferred_reenq_local.node)); + + exit_dsq(bypass_dsq(sch, cpu)); } free_percpu(sch->pcpu); @@ -5787,6 +5816,9 @@ static int alloc_kick_syncs(void) static void free_pnode(struct scx_sched_pnode *pnode) { + if (!pnode) + return; + exit_dsq(&pnode->global_dsq); kfree(pnode); } @@ -5798,7 +5830,10 @@ static struct scx_sched_pnode *alloc_pnode(struct scx_sched *sch, int node) if (!pnode) return NULL; - init_dsq(&pnode->global_dsq, SCX_DSQ_GLOBAL, sch); + if (init_dsq(&pnode->global_dsq, SCX_DSQ_GLOBAL, sch)) { + kfree(pnode); + return NULL; + } return pnode; } @@ -5809,7 +5844,7 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops, { struct scx_sched *sch; s32 level = parent ? parent->level + 1 : 0; - s32 node, cpu, ret; + s32 node, cpu, ret, bypass_fail_cpu = nr_cpu_ids; sch = kzalloc_flex(*sch, ancestors, level); if (!sch) @@ -5848,8 +5883,13 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops, goto err_free_pnode; } - for_each_possible_cpu(cpu) - init_dsq(bypass_dsq(sch, cpu), SCX_DSQ_BYPASS, sch); + for_each_possible_cpu(cpu) { + ret = init_dsq(bypass_dsq(sch, cpu), SCX_DSQ_BYPASS, sch); + if (ret) { + bypass_fail_cpu = cpu; + goto err_free_pcpu; + } + } for_each_possible_cpu(cpu) { struct scx_sched_pcpu *pcpu = per_cpu_ptr(sch->pcpu, cpu); @@ -5931,6 +5971,11 @@ static struct scx_sched *scx_alloc_and_add_sched(struct sched_ext_ops *ops, err_stop_helper: kthread_destroy_worker(sch->helper); err_free_pcpu: + for_each_possible_cpu(cpu) { + if (cpu == bypass_fail_cpu) + break; + exit_dsq(bypass_dsq(sch, cpu)); + } free_percpu(sch->pcpu); err_free_pnode: for_each_node_state(node, N_POSSIBLE) @@ -7173,7 +7218,7 @@ void __init init_sched_ext_class(void) int n = cpu_to_node(cpu); /* local_dsq's sch will be set during scx_root_enable() */ - init_dsq(&rq->scx.local_dsq, SCX_DSQ_LOCAL, NULL); + BUG_ON(init_dsq(&rq->scx.local_dsq, SCX_DSQ_LOCAL, NULL)); INIT_LIST_HEAD(&rq->scx.runnable_list); INIT_LIST_HEAD(&rq->scx.ddsp_deferred_locals); @@ -7872,11 +7917,21 @@ __bpf_kfunc s32 scx_bpf_create_dsq(u64 dsq_id, s32 node, const struct bpf_prog_a if (!dsq) return -ENOMEM; + /* + * init_dsq() must be called in GFP_KERNEL context. Init it with NULL + * @sch and update afterwards. + */ + ret = init_dsq(dsq, dsq_id, NULL); + if (ret) { + kfree(dsq); + return ret; + } + rcu_read_lock(); sch = scx_prog_sched(aux); if (sch) { - init_dsq(dsq, dsq_id, sch); + dsq->sched = sch; ret = rhashtable_lookup_insert_fast(&sch->dsq_hash, &dsq->hash_node, dsq_hash_params); } else { @@ -7884,8 +7939,10 @@ __bpf_kfunc s32 scx_bpf_create_dsq(u64 dsq_id, s32 node, const struct bpf_prog_a } rcu_read_unlock(); - if (ret) + if (ret) { + exit_dsq(dsq); kfree(dsq); + } return ret; }