Re: [PATCH 2/2] selftests/sched_ext: add cpuset DL rollback test

[Cheng-Yang Chou]

Hi Guopeng,

On Fri, Apr 17, 2026 at 11:37:42AM +0800, Guopeng Zhang wrote:
[...]
> +
> +#ifndef SYS_sched_setattr
> +#if defined(__x86_64__)
> +#define SYS_sched_setattr 314
> +#elif defined(__i386__)
> +#define SYS_sched_setattr 351
> +#elif defined(__aarch64__)

Nit: Since RISC-V uses the same assigned syscall number as ARM64, it
would be nice to support it here as well,

  +#elif defined(__aarch64__) || defined(__riscv)

> +#define SYS_sched_setattr 274
> +#else
> +#error "Unknown architecture: please define SYS_sched_setattr"
> +#endif
> +#endif

[...]

> +static enum scx_test_status run(void *arg)
> +{
> +	struct cpuset_dl_rollback_ctx *ctx = arg;
> +	char procs_path[PATH_MAX];
> +	long long before_bw, after_bw;
> +	int ret;
> +
> +	ret = read_cpu_total_bw(ctx->target_cpu, &before_bw);
> +	SCX_FAIL_IF(ret, "Failed to read baseline total_bw (%d)", ret);

The first read_cpu_total_bw() call is redundant because before_bw is
overwritten after spawn_dl_child(). Use a separate variable for the
baseline if needed. Otherwise, the second call already handles the same
error check.

> +
> +	ctx->link = bpf_map__attach_struct_ops(ctx->skel->maps.cpuset_dl_rollback_ops);
> +	SCX_FAIL_IF(!ctx->link, "Failed to attach scheduler");
> +
> +	ret = spawn_dl_child(ctx);
> +	switch (ret) {
> +	case -EACCES:
> +	case -EPERM:
> +		fprintf(stderr,
> +			"Skipping test: unable to place child in the source cgroup or enable SCHED_DEADLINE due to permissions (%d)\n",
> +			ret);
> +		return SCX_TEST_SKIP;
> +	case -EBUSY:
> +		fprintf(stderr,
> +			"Skipping test: SCHED_DEADLINE admission control rejected the child (%d)\n",
> +			ret);
> +		return SCX_TEST_SKIP;
> +	case -EINVAL:
> +		fprintf(stderr,
> +			"Skipping test: unable to enable SCHED_DEADLINE for the child in this environment (%d)\n",
> +			ret);
> +		return SCX_TEST_SKIP;
> +	}
> +	SCX_FAIL_IF(ret, "Failed to start SCHED_DEADLINE child (%d)", ret);
> +
> +	ret = read_cpu_total_bw(ctx->target_cpu, &before_bw);

Overwritten here.

> +	SCX_FAIL_IF(ret, "Failed to read pre-move total_bw (%d)", ret);

-- 
Thanks,
Cheng-Yang