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Mon, 1 Dec 2025 18:32:11 +0000 (GMT) From: Shrikanth Hegde To: mingo@kernel.org, peterz@infradead.org, vincent.guittot@linaro.org, linux-kernel@vger.kernel.org, kprateek.nayak@amd.com Cc: sshegde@linux.ibm.com, dietmar.eggemann@arm.com, vschneid@redhat.com, rostedt@goodmis.org, tglx@linutronix.de, tim.c.chen@linux.intel.com Subject: [PATCH 3/4] sched/fair: Check for blocked task after time check Date: Tue, 2 Dec 2025 00:01:45 +0530 Message-ID: <20251201183146.74443-4-sshegde@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251201183146.74443-1-sshegde@linux.ibm.com> References: <20251201183146.74443-1-sshegde@linux.ibm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-TM-AS-GCONF: 00 X-Authority-Analysis: v=2.4 cv=dK+rWeZb c=1 sm=1 tr=0 ts=692ddf31 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=wP3pNCr1ah4A:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=gfQPMJu-hSpRr0ZdjbEA:9 a=zZCYzV9kfG8A:10 X-Proofpoint-GUID: bQj7SX8pRlbw0qgQcDwC13oo7L8kb8WT X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTI5MDAyMCBTYWx0ZWRfXwbD5eyabvJLh jgC9Q5GNP+I3BwynKg6zu1bYf1gb0yTvEv5MyyDrr+Aala2rY4HZGc6/CfHuw/ll7maMWYxfvn8 Ip8TFsybKKzT2JDzcsOd9yuVOtFt8pFOBNh3h9CW6LjlZ0f8A0gvfvh6ESTJBOefb6d9/dvbjdl F0ZqSoW65rAlIURA6FXH4buUoMMakv9US5LuizxAl+IB/gXx+dFBDpLHc2nwDwdgihSC9JajXsP 95sE/xCrkkI1hv7gQ5o2zPsA5NXKm/FTSPV+pScT9+nfwMmI18dT5vGb9JzJod3whsR5rMaXupe M5Zs8Y41bmxP6/wzZQjH84iMzbiYoAE2IC9iS0UWLFYTOXwkh3w0krgmlQdyNIXAwRpUheW5ZSj bX/r4GzZv98R3C2FcdEihvYj4qeREA== X-Proofpoint-ORIG-GUID: bQj7SX8pRlbw0qgQcDwC13oo7L8kb8WT X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-28_08,2025-11-27_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 suspectscore=0 lowpriorityscore=0 clxscore=1015 priorityscore=1501 bulkscore=0 adultscore=0 phishscore=0 impostorscore=0 spamscore=0 malwarescore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511290020 Content-Type: text/plain; charset="utf-8" nohz.has_blocked can be updated often as and when CPUs enter idle state. But stats are updated only at regular intervals. Usually fixed to LOAD_AVG_PERIOD=3D32.=20 Read the value only after time check is successful to avoid cache references to it. Signed-off-by: Shrikanth Hegde --- kernel/sched/fair.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index 55746274af06..5534822fd754 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -12440,8 +12440,8 @@ static void nohz_balancer_kick(struct rq *rq) */ nohz_balance_exit_idle(rq); =20 - if (READ_ONCE(nohz.has_blocked) && - time_after(now, READ_ONCE(nohz.next_blocked))) + if (time_after(now, READ_ONCE(nohz.next_blocked)) && + READ_ONCE(nohz.has_blocked)) flags =3D NOHZ_STATS_KICK; =20 if (time_before(now, nohz.next_balance)) --=20 2.43.0