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Date: Wed, 4 Mar 2026 06:23:57 -1000
From: Tejun Heo <tj@kernel.org>
To: Andrea Righi <arighi@nvidia.com>
Cc: David Vernet <void@manifault.com>, Changwoo Min <changwoo@igalia.com>,
	Emil Tsalapatis <emil@etsalapatis.com>,
	Daniel Hodges <hodgesd@meta.com>, sched-ext@lists.linux.dev,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched_ext: Document task ownership state machine
Message-ID: <aahcnV2xPabCGc-b@slm.duckdns.org>
References: <20260304153343.340285-1-arighi@nvidia.com>
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In-Reply-To: <20260304153343.340285-1-arighi@nvidia.com>

Hello,

On Wed, Mar 04, 2026 at 04:33:43PM +0100, Andrea Righi wrote:
> + * Task Ownership State Machine (sched_ext_entity->ops_state)
>   *
> + * The sched_ext core uses this state machine to track task ownership
> + * between the SCX core and the BPF scheduler. This allows the BPF
> + * scheduler to dispatch tasks without strict ordering requirements, while
> + * the SCX core safely rejects invalid dispatches.
>   *
> + * State Transitions
>   *
> + *       .------------> NONE (owned by SCX core)
> + *       |               |           ^
> + *       |       enqueue |           | direct dispatch
> + *       |               v           |
> + *       |           QUEUEING -------'
> + *       |               |
> + *       |       enqueue |
> + *       |     completes |
> + *       |               v
> + *       |            QUEUED (owned by BPF scheduler)
> + *       |               |           ^
> + *       |      dispatch |           | affinity changed
> + *       |               |           | (dispatch aborts)
> + *       |               v           |
> + *       |          DISPATCHING -----'
> + *       |               |
> + *       |      dispatch |
> + *       |     completes |
> + *       `---------------'

I don't think we transition tasks from DISPATCHING to QUEUED on affinity
changes. Not yet anyway, right?

Thanks.

-- 
tejun