linux-kernel - Re: [PATCH] sched_ext: create_dsq: Return -EEXIST on duplicate request

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Message-ID: <Z-RkfScRAanAPs79@slm.duckdns.org>
Date: Wed, 26 Mar 2025 10:33:01 -1000
From: Tejun Heo <tj@...nel.org>
To: Jake Hillion <jake@...lion.co.uk>
Cc: arighi@...dia.com, changwoo@...lia.com, sched-ext@...a.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: create_dsq: Return -EEXIST on duplicate
 request

On Tue, Mar 25, 2025 at 10:41:52PM +0000, Jake Hillion wrote:
> 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@...lion.co.uk>

Applied to sched_ext/for-6.15-fixes w/ stable cc'd.

Thanks.

-- 
tejun