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sched_ext: create_dsq: Return -EEXIST on duplicate request

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create_dsq and therefore the scx_bpf_create_dsq kfunc currently silently
ignore duplicate entries. As a sched_ext scheduler is creating each DSQ
for a different purpose this is surprising behaviour.

Replace rhashtable_insert_fast which ignores duplicates with
rhashtable_lookup_insert_fast that reports duplicates (though doesn't
return their value). The rest of the code is structured correctly and
this now returns -EEXIST.

Tested by adding an extra scx_bpf_create_dsq to scx_simple. Previously
this was ignored, now init fails with a -17 code. Also ran scx_lavd
which continued to work well.

Signed-off-by: Jake Hillion <jake@hillion.co.uk>
Acked-by: Andrea Righi <arighi@nvidia.com>
Fixes: f0e1a0643a ("sched_ext: Implement BPF extensible scheduler class")
Cc: stable@vger.kernel.org # v6.12+
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Jake Hillion 2025-03-25 22:41:52 +00:00 committed by Tejun Heo
parent 883cc35e9f
commit a8897ed852
1 changed files with 2 additions and 2 deletions
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4
kernel/sched/ext.c
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@ -4171,8 +4171,8 @@ static struct scx_dispatch_q *create_dsq(u64 dsq_id, int node)
init_dsq(dsq, dsq_id);
ret = rhashtable_insert_fast(&dsq_hash, &dsq->hash_node,
dsq_hash_params);
ret = rhashtable_lookup_insert_fast(&dsq_hash, &dsq->hash_node,
dsq_hash_params);
if (ret) {
kfree(dsq);
return ERR_PTR(ret);