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Fri, 9 Jan 2026 03:20:08 +0000 From: Aaron Tomlin To: mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com Cc: sshegde@linux.ibm.com, neelx@suse.com, sean@ashe.io, mproche@gmail.com, linux-kernel@vger.kernel.org Subject: [PATCH 1/1] sched/deadline: Log Fair Server re-enablement for symmetry with debugfs Date: Thu, 8 Jan 2026 22:19:59 -0500 Message-ID: <20260109031959.2786873-2-atomlin@atomlin.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260109031959.2786873-1-atomlin@atomlin.com> References: <20260109031959.2786873-1-atomlin@atomlin.com> Content-Transfer-Encoding: quoted-printable X-ClientProxiedBy: BN0PR04CA0050.namprd04.prod.outlook.com (2603:10b6:408:e8::25) To CWLP123MB3523.GBRP123.PROD.OUTLOOK.COM (2603:10a6:400:70::10) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: CWLP123MB3523:EE_|LO0P123MB6446:EE_ X-MS-Office365-Filtering-Correlation-Id: de03d8a4-adc9-4dc7-f6c3-08de4f2dfde4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|7416014|376014|1800799024|366016; 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charset="utf-8" Currently, the scheduler's debug interface emits a notification to the console when the Fair Server is explicitly disabled via the fair_server sysfs attribute. However, no corresponding log entry is generated when the server is subsequently re-enabled. This omission results in an asymmetry within the kernel logs, potentially obscuring the true operational state of the scheduler during debugging or performance analysis. This patch amends dl_server_apply_params() to introduce the requisite logging. By detecting the transition from zero to non-zero bandwidth - strictly for the Fair Server entity and excluding initialisation - we ensure that a "Fair server re-enabled" message is emitted. This restores logging symmetry and provides administrators with a clear audit trail of manual runtime adjustments. Signed-off-by: Aaron Tomlin --- kernel/sched/deadline.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 319439fe1870..e64fb988e957 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1867,6 +1867,7 @@ int dl_server_apply_params(struct sched_dl_entity *dl= _se, u64 runtime, u64 perio u64 old_bw =3D init ? 0 : to_ratio(dl_se->dl_period, dl_se->dl_runtime); u64 new_bw =3D to_ratio(period, runtime); struct rq *rq =3D dl_se->rq; + bool fair_server =3D dl_se =3D=3D &rq->fair_server; int cpu =3D cpu_of(rq); struct dl_bw *dl_b; unsigned long cap; @@ -1876,6 +1877,11 @@ int dl_server_apply_params(struct sched_dl_entity *d= l_se, u64 runtime, u64 perio dl_b =3D dl_bw_of(cpu); guard(raw_spinlock)(&dl_b->lock); =20 + /* Symmetric to disable message in sched_fair_server_write() */ + if (!init && fair_server && !old_bw && new_bw) + printk_deferred("Fair server re-enabled on CPU %d.\n", + cpu); + cpus =3D dl_bw_cpus(cpu); cap =3D dl_bw_capacity(cpu); =20 --=20 2.51.0