From 63fb3ec80516b256e9fc91de48567f5eda61d135 Mon Sep 17 00:00:00 2001 From: Tejun Heo Date: Thu, 26 Sep 2024 12:56:46 -1000 Subject: [PATCH] sched_ext: Allow only user DSQs for scx_bpf_consume(), scx_bpf_dsq_nr_queued() and bpf_iter_scx_dsq_new() SCX_DSQ_GLOBAL is special in that it can't be used as a priority queue and is consumed implicitly, but all BPF DSQ related kfuncs could be used on it. SCX_DSQ_GLOBAL will be split per-node for scalability and those operations won't make sense anymore. Disallow SCX_DSQ_GLOBAL on scx_bpf_consume(), scx_bpf_dsq_nr_queued() and bpf_iter_scx_dsq_new(). This means that SCX_DSQ_GLOBAL can only be used as a dispatch target from BPF schedulers. With scx_flatcg, which was using SCX_DSQ_GLOBAL as the fallback DSQ, updated, this shouldn't affect any schedulers. This leaves find_dsq_for_dispatch() the only user of find_non_local_dsq(). Open code and remove find_non_local_dsq(). Signed-off-by: tejun heo Acked-by: David Vernet --- kernel/sched/ext.c | 22 ++++++++-------------- 1 file changed, 8 insertions(+), 14 deletions(-) diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c index d74d1fe06999e..ed2b914c42d15 100644 --- a/kernel/sched/ext.c +++ b/kernel/sched/ext.c @@ -1808,16 +1808,6 @@ static struct scx_dispatch_q *find_user_dsq(u64 dsq_id) return rhashtable_lookup_fast(&dsq_hash, &dsq_id, dsq_hash_params); } -static struct scx_dispatch_q *find_non_local_dsq(u64 dsq_id) -{ - lockdep_assert(rcu_read_lock_any_held()); - - if (dsq_id == SCX_DSQ_GLOBAL) - return &scx_dsq_global; - else - return find_user_dsq(dsq_id); -} - static struct scx_dispatch_q *find_dsq_for_dispatch(struct rq *rq, u64 dsq_id, struct task_struct *p) { @@ -1835,7 +1825,11 @@ static struct scx_dispatch_q *find_dsq_for_dispatch(struct rq *rq, u64 dsq_id, return &cpu_rq(cpu)->scx.local_dsq; } - dsq = find_non_local_dsq(dsq_id); + if (dsq_id == SCX_DSQ_GLOBAL) + dsq = &scx_dsq_global; + else + dsq = find_user_dsq(dsq_id); + if (unlikely(!dsq)) { scx_ops_error("non-existent DSQ 0x%llx for %s[%d]", dsq_id, p->comm, p->pid); @@ -6176,7 +6170,7 @@ __bpf_kfunc bool scx_bpf_consume(u64 dsq_id) flush_dispatch_buf(dspc->rq); - dsq = find_non_local_dsq(dsq_id); + dsq = find_user_dsq(dsq_id); if (unlikely(!dsq)) { scx_ops_error("invalid DSQ ID 0x%016llx", dsq_id); return false; @@ -6497,7 +6491,7 @@ __bpf_kfunc s32 scx_bpf_dsq_nr_queued(u64 dsq_id) goto out; } } else { - dsq = find_non_local_dsq(dsq_id); + dsq = find_user_dsq(dsq_id); if (dsq) { ret = READ_ONCE(dsq->nr); goto out; @@ -6546,7 +6540,7 @@ __bpf_kfunc int bpf_iter_scx_dsq_new(struct bpf_iter_scx_dsq *it, u64 dsq_id, if (flags & ~__SCX_DSQ_ITER_USER_FLAGS) return -EINVAL; - kit->dsq = find_non_local_dsq(dsq_id); + kit->dsq = find_user_dsq(dsq_id); if (!kit->dsq) return -ENOENT;