Re: [PATCH] sched_ext: Close the pre-enable ops error claim window

Re: [PATCH] sched_ext: Close the pre-enable ops error claim window

[Tejun Heo]

Hello, Qiurong.

On Thu, Sep 10, 2026 at 04:45:33PM +0800, Qiurong Fang wrote:
> +		if (scx_tryset_enable_state(SCX_DISABLED, SCX_DISABLING))
> +			goto done;
> +		break;

Please drop this hunk. Once SCX_ENABLING precedes ops->priv publication,
scx_tryset_enable_state() cannot fail here.

> +	if (!scx_tryset_enable_state(SCX_ENABLING, SCX_DISABLED)) {
> +		pr_warn("sched_ext: enable raced with a state transition, aborting\n");
> +		ret = -EBUSY;

This failure path is also unreachable. The state was checked as SCX_DISABLED
under scx_enable_mutex, and no disable can start before publication. Please
move the existing transition and retain the reset on allocation failure.

Thanks.

-- 
tejun

Re: [PATCH v2] sched_ext: Close the pre-enable ops error claim window

[Tejun Heo]

Hello, Qiurong.

On Fri, Sep 11, 2026 at 10:42:56AM +0800, Qiurong Fang wrote:
> +		scx_tryset_enable_state(SCX_DISABLED, SCX_ENABLING);

All allocation failures precede ops->priv publication, so no disable can
race here and the state must still be SCX_ENABLING. Please use:

        WARN_ON_ONCE(scx_set_enable_state(SCX_DISABLED) != SCX_ENABLING);

Please also update the moved comment. Allocation failure still unwinds
locally. Full disabling on failure applies only after
scx_alloc_and_add_sched() succeeds.

Thanks.

-- 
tejun