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[36.225.72.95]) by smtp.gmail.com with ESMTPSA id 586e51a60fabf-439fc4dcb89sm4333601fac.12.2026.05.15.07.37.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 15 May 2026 07:37:02 -0700 (PDT) Date: Fri, 15 May 2026 22:36:58 +0800 From: Cheng-Yang Chou To: Tejun Heo Cc: sched-ext@lists.linux.dev, David Vernet , Andrea Righi , Changwoo Min , Kuba Piecuch , Ching-Chun Huang , Chia-Ping Tsai Subject: Re: [PATCH v3 1/2] sched_ext: Add dispatch transaction API Message-ID: <20260515221149.Gaf09@cchengyang.duckdns.org> References: <20260509191223.168648-1-yphbchou0911@gmail.com> <20260509191223.168648-2-yphbchou0911@gmail.com> Precedence: bulk X-Mailing-List: sched-ext@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hi Tejun, On Sun, May 10, 2026 at 04:06:19AM -1000, Tejun Heo wrote: > On Sun, May 10, 2026 at 03:11:56AM +0800, Cheng-Yang Chou wrote: > > -static void scx_dsq_insert_commit(struct scx_sched *sch, struct task_struct *p, > > - u64 dsq_id, u64 enq_flags) > > +static void scx_dsq_insert_buf(struct scx_sched *sch, struct task_struct *p, > > + u64 dsq_id, u64 enq_flags, unsigned long qseq) > > Please don't mix rename and functional changes in the same patch. Can we do > scx_dsq_insert_stage() instead? Seperated into its own commit using scx_diq_insert_stage() in v4. > > > +/** > > + * scx_bpf_dsq_insert_commit - Commit a dispatch transaction > > + * @p: task_struct to insert > > + * @dsq_id: DSQ to insert into > > + * @enq_flags: SCX_ENQ_* > > + * @token: token from scx_bpf_dsq_insert_begin() > > + * @aux: implicit BPF argument > > + * > > + * Like scx_bpf_dsq_insert() with slice=0, but commits a dispatch transaction > > + * begun with scx_bpf_dsq_insert_begin(). If @p was dequeued or claimed > > + * between begin and commit, the dispatch is silently discarded. Use > > + * scx_bpf_task_set_slice() to set a non-default slice. > > + * > > + * Returns %true if the entry was buffered for dispatch, %false on preamble > > + * failure (e.g. @p is not owned by this scheduler). Note: stale token > > + * detection fires asynchronously in finish_dispatch() after ops.dispatch() > > + * returns. A %true return does not guarantee the task was actually dispatched. > > + */ > > I think this needs more detailed documentation. It's difficult to tell what > it provides and why one would want to use it from the above and it's a > pretty subtle thing. Expanded in v4, the kdoc now covers the race scenario where scx_bpf_dsq_insert() misses pre-dispatch validity checks, the intended usage with ops.dequeue(), and the caveat that a %true return doesn't guarantee actual dispatch. Thanks. -- Cheers, Cheng-Yang