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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-cb258ff402asm1631213a12.22.2026.07.16.04.52.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 16 Jul 2026 04:52:05 -0700 (PDT) From: Zhongqiu Han To: rafael@kernel.org, viresh.kumar@linaro.org, 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, kprateek.nayak@amd.com, christian.loehle@arm.com, liaochang1@huawei.com Cc: linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, zhongqiu.han@oss.qualcomm.com, stable@vger.kernel.org Subject: [PATCH] cpufreq: schedutil: Publish util hooks only after all sg_cpu are initialized Date: Thu, 16 Jul 2026 19:51:58 +0800 Message-ID: <20260716115159.848403-1-zhongqiu.han@oss.qualcomm.com> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: linux-pm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Authority-Analysis: v=2.4 cv=PsejqQM3 c=1 sm=1 tr=0 ts=6a58c5e6 cx=c_pps a=rz3CxIlbcmazkYymdCej/Q==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=RAioF0-LDSMA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=yOCtJkima9RkubShWh1s:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=cKKUN8DYBXwKWaGdE6wA:9 a=bFCP_H2QrGi7Okbo017w:22 X-Proofpoint-GUID: KHClrvtu1opFMC7r5kZiFxUyd2LtGvXi X-Proofpoint-Spam-Info: AW1haW4tMjYwNzE2MDEyMiBTYWx0ZWRfX/GNmY4W46FTO JMITcVLxV7uoWB0ogmLupZID1dusNjHnPJ+HxUZuA8QDM/Qv4R00mrIRerNkl0yrFPN8xwhaQZZ AYDQEh2C56au1HOecUNVjGWZKEpMImY= X-Proofpoint-ORIG-GUID: KHClrvtu1opFMC7r5kZiFxUyd2LtGvXi X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNzE2MDEyMiBTYWx0ZWRfXxH02hShUAaGN goTTT878HUXk6ikHlih4cXGaMqB0cZdMj3nsObusWNqBWOrU2EIlj+Dm3fSw0S+816pRug6dUYd /GT5Bgn5HM3nS4YrPQqgnHsFC/LzW+0f1t49FyatFvti5NVQ9IcsGcpw9tUX6Ngxgw5eUj3EAu+ EXwltKWgcJk1Opnx7MkGFWc1hAAv7o8FqB9w08i9eOg4A9fN8oKqnbZUQbYRVn+asltFkqwpybs BcEh4PNRnIBuQi7cXv4cmgnjAy47Ze+gwaWzQ6+z7iUrlVlWWpce+lm7/F1Z7uEm+3I9qLbMcsg uzz/BZQHCMD6pHtYDFH4zjBKm8wna7kO5Z/+jI3ijThnO2wFdqwJBn3Er9irD1pMnKi45qBt4BK PdKu8aCW9UO4gMhPVGlQRKdBtB8kGbGQaCDiLe00N9mbLSC2gltFy1niCovXnyNuKysq2MUBNkV 2iI5U7M5Vz0fL9hUBJA== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.134,FMLib:17.12.100.49 definitions=2026-07-16_04,2026-07-15_02,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 malwarescore=0 clxscore=1015 bulkscore=0 priorityscore=1501 lowpriorityscore=0 adultscore=0 suspectscore=0 spamscore=0 phishscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2606150000 definitions=main-2607160122 Commit 16a03c71bba0 ("cpufreq: schedutil: Merge initialization code of sg_cpu in single loop") merged the per-CPU initialization and the utilization-hook registration into a single loop in sugov_start(). For a shared cpufreq policy this re-introduces the race originally fixed by commit ab2f7cf141aa ("cpufreq: schedutil: Fix sugov_start() versus sugov_update_shared() race"). The scheduler's util path reaches the hook under RCU-sched and never takes policy->rwsem, so the rwsem held across sugov_start() cannot serialize the two. Once the first CPU's hook is published, sugov_update_shared() may run and, via sugov_next_freq_shared(), read/write each sibling sugov_cpu (iowait_boost, util, bw_min, ...) concurrently with the memset() still initializing them, with no lock common to both sides: the update side holds sg_policy->update_lock while the init side holds only policy->rwsem, which the scheduler's util path never takes. The walk only accesses scalar members, never a pointer like ->sg_policy, so it does not crash today; it merely uses stale (or zero on first start) values that skew the frequency selection and tracepoints. It is still a genuine data race, and a latent crash once any pointer member is dereferenced there. Restore the two-phase approach: initialize all per-CPU structures first, and only then publish the per-CPU utilization update hooks. Fixes: 16a03c71bba0 ("cpufreq: schedutil: Merge initialization code of sg_cpu in single loop") Cc: stable@vger.kernel.org Signed-off-by: Zhongqiu Han --- kernel/sched/cpufreq_schedutil.c | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c index dc0835ceee98..6ad080de8644 100644 --- a/kernel/sched/cpufreq_schedutil.c +++ b/kernel/sched/cpufreq_schedutil.c @@ -872,8 +872,19 @@ static int sugov_start(struct cpufreq_policy *policy) memset(sg_cpu, 0, sizeof(*sg_cpu)); sg_cpu->cpu = cpu; sg_cpu->sg_policy = sg_policy; + } + + /* + * Publish the hooks only after all per-CPU data is initialized, so a + * shared policy's sugov_update_shared() never reads an uninitialized + * sibling sugov_cpu. + */ + for_each_cpu(cpu, policy->cpus) { + struct sugov_cpu *sg_cpu = &per_cpu(sugov_cpu, cpu); + cpufreq_add_update_util_hook(cpu, &sg_cpu->update_util, uu); } + return 0; } -- 2.43.0