Commit 63fb3ec8 authored by Tejun Heo's avatar Tejun Heo
Browse files

sched_ext: Allow only user DSQs for scx_bpf_consume(), scx_bpf_dsq_nr_queued()... 


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: default avatartejun heo <tj@kernel.org>
Acked-by: default avatarDavid Vernet <void@manifault.com>
parent c9c809f4

kernel/sched/ext.c

+8 −14
Original line number Diff line number Diff line
@@ -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;