From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=158.69.130.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794164068; b=yZ2F7kCf9nKWVQUHNpLdAak8+a47nnF7vFgJ59m/OcOWCPlPALrVR0zcJ2yONMgScYC7 rzXnMBpqLUlKFeXhNnIPrzGxiVZlMZTl1eaMvUlSBDwt+T1KVClDB9M6lxRDBbiEUDfHN Vg+PkQBJZzfxGfI+yXoLfZ+T4pXOHljDvgczmtgFS5CDK/AeVXo6aje+C0bd+e0huEVf4 2vX0A3NWORbLhEs3UYs5O4RkSQDpWL4DGDmDn8ogYpeIFN1JwMghKsBH/yfv0ED8nbTuy KDa2EzD5F3nVYucPxfbtWLu+k6zmAoE98AscGWpn/PYrc/lcCOHrzB8j6PmRxEXGAog== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794164068; h=DMARC-Filter:DKIM-Signature:Received:From:To:Cc:Subject:Date: Message-Id:X-Mailer:In-Reply-To:References:MIME-Version: Content-Transfer-Encoding; bh=eC94u6hDuVR5e/ux+QurOxV6RQO2Prbl2yuzY3/UcgQ=; b=b7Wac1cPv70Pcw2C+TCpZyOWqqGT5ajYL8te1LjOX5zqllyiQEQDUgMDwLIqK7COg5bF /TelWQWiKQswTyOQFur+hL7ufs6vuB7x37D1gaH4PqsxmJ+Bbp2j+fZr2vMqhPm5+1b9M hHmxFkYJa3iy1BMw2NuXqx0Prqz4SX7RzvY5iXUlcEmO7LjdGSIbKiSfiKaKI0A7E5YiE UTOXovaxLrnAhQRT/77PPw13PK8XTeXtlh28CtSIHBFi9nxDf/sGzbXn4v4CB8UfLaoRQ p1R6ptGU23N8xHQ6LPMbyxQOgtHSOTYJubhGAAgYvHYeP6ohwmy9zLfi+S3AZBJNIOA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=efficios.com; spf=pass smtp.mailfrom=efficios.com; dkim=pass header.d=efficios.com header.i=@efficios.com header.a=rsa-sha256 header.s=smtpout1 header.b=GrZseIx8; arc=none smtp.remote-ip=158.69.130.18 Received: from smtpout.efficios.com (smtpout.efficios.com [158.69.130.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B1F816083633; Sun, 8 Nov 2026 18:54:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org B1F816083633 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=efficios.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=efficios.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=efficios.com header.i=@efficios.com header.a=rsa-sha256 header.s=smtpout1 header.b=GrZseIx8 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=efficios.com; s=smtpout1; t=1794164066; bh=eC94u6hDuVR5e/ux+QurOxV6RQO2Prbl2yuzY3/UcgQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=GrZseIx87XhImroHVRZVfKCBPsw2xbJPlQpxcwVHt6c3xXk/sEALKdTmx8j7Yn7rr 4FgRL7ZnkPB91wvTvBCLqHYmnm/4gX35COK3PVl9v+fMw7cXHX65aYeFS0uokqNKJf GgkqolTGummUOI0MVIzylwGHH71oZW3/KuIqzp3544wfnG6LUOWZ16pROyN7D+YOg1 JfC2873UmZhv9NJ2ts/LRz5zLSx95YT80nB4UGwN8TiJRqx0MNVtnZjsJw4dqoxq3v LA8rNDkqBrUjDmgeptsuAMQEYvSYZpPOigFCrufrBwWwHSlu3cBZS9Np1YyXi3fbEO QHgUt7iu4WYtA== Received: from thinkos.internal.efficios.com (unknown [64.58.40.251]) by smtpout.efficios.com (Postfix) with ESMTPSA id 4jN2C64l0bzM61; Sun, 08 Nov 2026 13:54:26 -0500 (EST) From: Mathieu Desnoyers To: juri.lelli@redhat.com, peterz@infradead.org, mingo@redhat.com, vincent.guittot@linaro.org Cc: linux-kernel@vger.kernel.org, Mathieu Desnoyers , tglx@kernel.org, will@kernel.org, boqun@kernel.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, luca.abeni@santannapisa.it, mathieu.poirier@linaro.org, longman@redhat.com, ridong.chen@linux.dev, tj@kernel.org, hannes@cmpxchg.org, mkoutny@suse.com, shuah@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, parri.andrea@gmail.com, m.szyprowski@samsung.com, kayracizmeci@gmail.com, weihengqiuu@gmail.com, cgroups@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-rt-devel@lists.linux.dev, stable@vger.kernel.org Subject: [PATCH v5 25/29] sched/deadline: Count the bandwidth a boosted task is given Date: Sun, 8 Nov 2026 13:54:02 -0500 Message-Id: <20261108185406.1549770-26-mathieu.desnoyers@efficios.com> X-Mailer: git-send-email 2.39.5 In-Reply-To: <20261108185406.1549770-1-mathieu.desnoyers@efficios.com> References: <20261108185406.1549770-1-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-Transfer-Encoding: 8bit sched_setattr(SCHED_DEADLINE) on a sleeping task that priority inheritance boosted into the class leaves the new bandwidth out of this_bw. switched_to_dl() does not run, since the task is in the class already. sched_dl_overflow() changes this_bw only for a task of the deadline policy. When the task wakes up, __add_running_bw() warns: WARN_ON_ONCE(dl_rq->running_bw > dl_rq->this_bw); When the task leaves the runqueue, this_bw would stay short by that bandwidth, and skew GRUB reclaiming on that CPU. Fix this by changing this_bw in __setparam_dl(), which every task that gains deadline parameters goes through. If no runqueue counts the bandwidth of the task, dl_change_utilization() now adds the new one. It now also runs when the bandwidth does not change. It then returns early, so that a sleeping task keeps its running_bw and its inactive timer. A sugov kthread given a reservation of its own now has its bandwidth counted in this_bw. It reaches dl_change_utilization(), so the WARN_ON_ONCE() for SCHED_FLAG_SUGOV there goes. sched_dl_overflow() returned early for an unchanged bandwidth, even if no root domain counts it. That is the case for such a kthread, and for a task that a rebuild left out. Admit such a bandwidth as new. Without room, that fails with EBUSY. The Sashiko AI review of the third posting found this early return. A reproducer shows the warning, and this_bw unchanged by the change. With this patch, this_bw takes the new bandwidth, and nothing warns. Fixes: 8fd27231c330 ("sched/deadline: Track the "total rq utilization" too") Cc: stable@vger.kernel.org Signed-off-by: Mathieu Desnoyers --- kernel/sched/deadline.c | 54 ++++++++++++++++++++++++++++++++--------- 1 file changed, 43 insertions(+), 11 deletions(-) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 47adff100392..bc76203ab506 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -507,22 +507,37 @@ void cancel_inactive_timer(struct sched_dl_entity *dl_se) cancel_dl_timer(dl_se, &dl_se->inactive_timer); } +/* + * Make the runqueue of a sleeping task count @new_bw as the bandwidth of + * the task. Do nothing for a queued task. The dequeue and the enqueue + * around the change of its parameters update this_bw. + */ static void dl_change_utilization(struct task_struct *p, u64 new_bw) { - WARN_ON_ONCE(p->dl.flags & SCHED_FLAG_SUGOV); + struct sched_dl_entity *dl_se = &p->dl; + struct rq *rq = task_rq(p); if (task_on_rq_queued(p)) return; /* - * The task is waking up on another CPU, and no runqueue counts its - * bandwidth. The enqueue adds it, with the new parameters that - * __setparam_dl() sets right after this. + * No runqueue counts the bandwidth of the task. Add the new one to + * this runqueue, so that add_rq_bw() adds nothing later. A task that + * enters the class asleep comes here, and so does a special entity + * given a reservation of its own. So does a task waking up on + * another CPU: task_cpu() already points at the CPU it wakes on. */ - if (!p->dl.dl_bw_oncpu) + if (!dl_se->dl_bw_oncpu) { + __add_rq_bw(new_bw, &rq->dl); + dl_se->dl_bw_oncpu = 1; + return; + } + + /* Same bandwidth: leave running_bw and the inactive timer alone. */ + if (new_bw == dl_se->dl_bw) return; - dl_rq_change_utilization(task_rq(p), &p->dl, new_bw); + dl_rq_change_utilization(rq, dl_se, new_bw); } static void __dl_clear_params(struct sched_dl_entity *dl_se); @@ -4407,10 +4422,6 @@ int sched_dl_overflow(struct task_struct *p, int policy, if (attr->sched_flags & SCHED_FLAG_SUGOV) return 0; - /* !deadline task may carry old deadline bandwidth */ - if (new_bw == p->dl.dl_bw && task_has_dl_policy(p)) - return 0; - /* * Change the bandwidth of a deadline task where it is counted: in * the root domain of the CPU recorded with it. A task moved asleep @@ -4425,6 +4436,16 @@ int sched_dl_overflow(struct task_struct *p, int policy, */ counted = task_has_dl_policy(p) && p->dl.dl_bw_cpu >= 0 && p->dl.dl_bw_gen == dl_bw_gen; + + /* + * !deadline task may carry old deadline bandwidth. The same + * bandwidth needs no admission if it is counted. If it is not, admit + * it as new below. A special entity given a reservation of its own + * has no bandwidth counted, nor has a task that a rebuild left out. + */ + if (new_bw == p->dl.dl_bw && counted) + return 0; + cpu = counted && p->dl.dl_bw ? p->dl.dl_bw_cpu : task_cpu(p); dl_b = dl_bw_of(cpu); @@ -4454,7 +4475,6 @@ int sched_dl_overflow(struct task_struct *p, int policy, if (counted) __dl_sub(dl_b, p->dl.dl_bw, cpus); __dl_add(dl_b, new_bw, cpus); - dl_change_utilization(p, new_bw); err = 0; } else if (!dl_policy(policy) && task_has_dl_policy(p)) { /* @@ -4504,6 +4524,18 @@ int sched_dl_overflow(struct task_struct *p, int policy, void __setparam_dl(struct task_struct *p, const struct sched_attr *attr) { struct sched_dl_entity *dl_se = &p->dl; + u64 period = attr->sched_period ?: attr->sched_deadline; + + /* + * Change the bandwidth that the runqueue counts here, with the + * parameters. A task that priority inheritance boosted into the + * class is in it already, so switched_to_dl() does not run for it. + * + * A special entity has no bandwidth on a runqueue. Test the flags + * of the request, since those of the entity are still the old ones. + */ + if (!(attr->sched_flags & SCHED_FLAG_SUGOV)) + dl_change_utilization(p, to_ratio(period, attr->sched_runtime)); dl_se->dl_runtime = attr->sched_runtime; dl_se->dl_deadline = attr->sched_deadline; -- 2.47.3