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Thu, 05 Nov 2026 02:20:04 -0800 (PST) X-Received: by 2002:a05:6000:4027:b0:48d:fbdd:4132 with SMTP id ffacd0b85a97d-48e6e4f540bmr39671524f8f.18.1793874004043; Thu, 05 Nov 2026 02:20:04 -0800 (PST) Received: from jlelli-thinkpadt14gen4.remote.csb ([151.29.158.90]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48fea180ee1sm10646770f8f.4.2026.11.05.02.20.02 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 05 Nov 2026 02:20:03 -0800 (PST) Date: Thu, 5 Nov 2026 11:20:01 +0100 From: Juri Lelli To: Mathieu Desnoyers Cc: Peter Zijlstra , Ingo Molnar , Vincent Guittot , linux-kernel@vger.kernel.org, Dietmar Eggemann , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , K Prateek Nayak , Luca Abeni , Mathieu Poirier , Waiman Long , Ridong Chen , Tejun Heo , Johannes Weiner , Michal =?iso-8859-1?Q?Koutn=FD?= , Shuah Khan , Sebastian Andrzej Siewior , Clark Williams , cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH v2 03/21] sched/deadline: Do not admit bandwidth for parameters that are kept Message-ID: References: <20261104211207.1392343-1-mathieu.desnoyers@efficios.com> <20261104211207.1392343-4-mathieu.desnoyers@efficios.com> X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20261104211207.1392343-4-mathieu.desnoyers@efficios.com> Hello, On 04/11/26 16:11, Mathieu Desnoyers wrote: > sys_sched_setattr() fills a SCHED_FLAG_KEEP_PARAMS request in from the > task itself (get_params()), with no lock held, and > __sched_setscheduler() then skips __setscheduler_params(): the task > keeps the parameters it has, and its dl_bw with them. > sched_dl_overflow() runs all the same. > > A parameter change of the task's own that lands in between leaves the > request stale, and dl_param_changed() takes it for a change: total_bw of > the root domain, and this_bw and running_bw of its runqueue through > dl_change_utilization(), then hold a bandwidth the task does not have, > and the release at its 0-lag time, which takes the task's own dl_bw, > leaves the difference behind. > > There is nothing to admit for parameters that are kept: skip the check. > > Found by reading, after the Sashiko AI review of the first posting of > this series raised the case the previous patch refuses. Not reproduced: > it needs a parameter change of a deadline task to land inside the window > of a SCHED_FLAG_KEEP_PARAMS request on the same task. > > Fixes: a509a7cd7974 ("sched/uclamp: Extend sched_setattr() to support utilization clamping") > Signed-off-by: Mathieu Desnoyers > --- Reviewed-by: Juri Lelli Thanks, Juri