linux-kernel - Re: [PATCH v2 1/1] sched_ext: Add error logging for dsq creation failures

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Message-ID: <aWDUbVsJXth8KuqW@gpd4>
Date: Fri, 9 Jan 2026 11:11:57 +0100
From: Andrea Righi <arighi@...dia.com>
To: George Guo <dongtai.guo@...ux.dev>
Cc: changwoo@...lia.com, etsal@...a.com, guodongtai@...inos.cn,
	linux-kernel@...r.kernel.org, sched-ext@...ts.linux.dev,
	tj@...nel.org, void@...ifault.com
Subject: Re: [PATCH v2 1/1] sched_ext: Add error logging for dsq creation
 failures

On Fri, Jan 09, 2026 at 06:03:58PM +0800, George Guo wrote:
> From: George Guo <guodongtai@...inos.cn>
> 
> Add scx_bpf_error() calls when scx_bpf_create_dsq() fails in multiple
> schedulers to improve debuggability:
> 
> - scx_central.bpf.c: central_init()
> - scx_flatcg.bpf.c: fcg_cgroup_init() and fcg_init()
> - scx_qmap.bpf.c: qmap_init()
> 
> Signed-off-by: George Guo <guodongtai@...inos.cn>

Huh? No, we already get an error message both in dmesg and in stdout when
scx_bpf_create_dsq() fails, so I don't think this is required.

Are you sure you were not hitting other issues when your scheduler failed
to load silently?

Thanks,
-Andrea

> ---
>  tools/sched_ext/scx_central.bpf.c | 4 +++-
>  tools/sched_ext/scx_flatcg.bpf.c  | 4 +++-
>  tools/sched_ext/scx_qmap.bpf.c    | 8 ++++++--
>  3 files changed, 12 insertions(+), 4 deletions(-)
> 
> diff --git a/tools/sched_ext/scx_central.bpf.c b/tools/sched_ext/scx_central.bpf.c
> index 55df8b798865..1c2376b75b5d 100644
> --- a/tools/sched_ext/scx_central.bpf.c
> +++ b/tools/sched_ext/scx_central.bpf.c
> @@ -301,8 +301,10 @@ int BPF_STRUCT_OPS_SLEEPABLE(central_init)
>  	int ret;
>  
>  	ret = scx_bpf_create_dsq(FALLBACK_DSQ_ID, -1);
> -	if (ret)
> +	if (ret) {
> +		scx_bpf_error("scx_bpf_create_dsq failed (%d)", ret);
>  		return ret;
> +	}
>  
>  	timer = bpf_map_lookup_elem(&central_timer, &key);
>  	if (!timer)
> diff --git a/tools/sched_ext/scx_flatcg.bpf.c b/tools/sched_ext/scx_flatcg.bpf.c
> index 43126858b8e4..c216480c3ee0 100644
> --- a/tools/sched_ext/scx_flatcg.bpf.c
> +++ b/tools/sched_ext/scx_flatcg.bpf.c
> @@ -842,8 +842,10 @@ int BPF_STRUCT_OPS_SLEEPABLE(fcg_cgroup_init, struct cgroup *cgrp,
>  	 * unlikely case that it breaks.
>  	 */
>  	ret = scx_bpf_create_dsq(cgid, -1);
> -	if (ret)
> +	if (ret) {
> +		scx_bpf_error("scx_bpf_create_dsq failed (%d)", ret);
>  		return ret;
> +	}
>  
>  	cgc = bpf_cgrp_storage_get(&cgrp_ctx, cgrp, 0,
>  				   BPF_LOCAL_STORAGE_GET_F_CREATE);
> diff --git a/tools/sched_ext/scx_qmap.bpf.c b/tools/sched_ext/scx_qmap.bpf.c
> index df21fad0c438..5fdd83769405 100644
> --- a/tools/sched_ext/scx_qmap.bpf.c
> +++ b/tools/sched_ext/scx_qmap.bpf.c
> @@ -866,12 +866,16 @@ s32 BPF_STRUCT_OPS_SLEEPABLE(qmap_init)
>  		print_cpus();
>  
>  	ret = scx_bpf_create_dsq(SHARED_DSQ, -1);
> -	if (ret)
> +	if (ret) {
> +		scx_bpf_error("scx_bpf_create_dsq failed (%d)", ret);
>  		return ret;
> +	}
>  
>  	ret = scx_bpf_create_dsq(HIGHPRI_DSQ, -1);
> -	if (ret)
> +	if (ret) {
> +		scx_bpf_error("scx_bpf_create_dsq failed (%d)", ret);
>  		return ret;
> +	}
>  
>  	timer = bpf_map_lookup_elem(&monitor_timer, &key);
>  	if (!timer)
> -- 
> 2.49.0
>