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[103.229.16.4]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-c76c65935cbsm21622903a12.26.2026.04.09.04.14.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 09 Apr 2026 04:14:12 -0700 (PDT) From: Zhongqiu Han To: rafael@kernel.org, viresh.kumar@linaro.org Cc: venkatesh.pallipadi@intel.com, davej@redhat.com, trenn@suse.de, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org, zhongqiu.han@oss.qualcomm.com Subject: [PATCH v2 0/2] cpufreq: governor: Fix races and stale baseline on prev_cpu_nice Date: Thu, 9 Apr 2026 19:14:05 +0800 Message-ID: <20260409111407.9775-1-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-Proofpoint-ORIG-GUID: qmy9sC_4MIgJZG06Nqt6HjEPh4mbgH5n X-Proofpoint-GUID: qmy9sC_4MIgJZG06Nqt6HjEPh4mbgH5n X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNDA5MDA5NiBTYWx0ZWRfX5I9FLyiaGj8B vyMk5wGT5LfeQLJFkiiCBNA362YAe1vbgaZvUV4Rw7HEoYorBquv11424Xuv5YzAiHqtbE9KJLm DKzpVyqkpNazMmTq5FwOeI/Bta2hbrB9OctV88S4coqczXeL29DCeAl4Jxq7lgb5Wb5O1/0owjz A4ejwkOlmLW1DGSe7aaS8BKjuUQxcDuoo8xk11aBU9IDAQ8ImmcpJeMHWQ2gRsQsCgToqy39paE UTILmPWw1NbycQGiCot7Gx1GsRxc2YM+jTfKM6B13NOLifLUtykWAZ5DCnTmvluedINkCbF/HQH M4SCPjeDbtWzW+NPtJzF9ol6bm5TsBkM1q4Hj/aMnEDWAM966oJj9UuZf9euic/r2iGYfN2/ruk 0KBVPZpJXKtvcyeHceRHVv1uXws5vITI3QJiXudIeSOMkWT1GdVAuhlUoSuMa2J/Sic2dyVLURy nhqeXlDGuIBNfA1Zj6w== X-Authority-Analysis: v=2.4 cv=BefoFLt2 c=1 sm=1 tr=0 ts=69d78a06 cx=c_pps a=oF/VQ+ItUULfLr/lQ2/icg==:117 a=nuhDOHQX5FNHPW3J6Bj6AA==:17 a=A5OVakUREuEA:10 a=s4-Qcg_JpJYA:10 a=VkNPw1HP01LnGYTKEx00:22 a=u7WPNUs3qKkmUXheDGA7:22 a=3WHJM1ZQz_JShphwDgj5:22 a=VwQbUJbxAAAA:8 a=EUspDBNiAAAA:8 a=kJhCsH8l8v12fBfCrQsA:9 a=3WC7DwWrALyhR5TkjVHa:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-04-09_03,2026-04-09_01,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 impostorscore=0 adultscore=0 suspectscore=0 spamscore=0 priorityscore=1501 phishscore=0 malwarescore=0 bulkscore=0 clxscore=1015 lowpriorityscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2604010000 definitions=main-2604090096 Patch 1 fixes a data race between sysfs store callbacks and the DBS work handler. gov_update_cpu_data() writes prev_cpu_idle and prev_cpu_nice while holding only attr_set->update_lock, whereas dbs_update() reads and writes the same fields while holding only policy_dbs->update_mutex. Because these are independent locks, the two paths are not mutually exclusive. The fix acquires policy_dbs->update_mutex inside gov_update_cpu_data() for each policy, and also holds it around the initialization loop in cpufreq_dbs_governor_start() to close a similar window against concurrent sysfs writes. Patch 2 fixes a stale-baseline spike on prev_cpu_nice that occurs when ignore_nice_load is enabled via sysfs. Because prev_cpu_nice is only advanced in dbs_update() when ignore_nice is true, it accumulates an unbounded debt of nice CPU time while ignore_nice is false. The moment ignore_nice_load is flipped to 1, the next dbs_update() computes a massive idle_time delta against the stale baseline, producing an incorrect CPU load value. The fix unconditionally samples and advances prev_cpu_nice on every dbs_update() call, regardless of ignore_nice, so the baseline is always current. As a consequence, the prev_cpu_nice reset in gov_update_cpu_data() and the gov_update_cpu_data() call in ignore_nice_load_store() are no longer needed and are removed. Changelog: - Update linux-next base - Based on v1 review, patch 1 is updated to add the missing protection around cpufreq_dbs_governor_start(), and patch 2/2 is added. - Link to v1: https://lore.kernel.org/all/20260406110113.3475920-1-zhongqiu.han@oss.qualcomm.com/ Zhongqiu Han (2): cpufreq: governor: Fix race between sysfs store and dbs work handler cpufreq: governor: Fix stale prev_cpu_nice spike when enabling ignore_nice_load drivers/cpufreq/cpufreq_conservative.c | 3 --- drivers/cpufreq/cpufreq_governor.c | 35 ++++++++++++++++++-------- drivers/cpufreq/cpufreq_ondemand.c | 3 --- 3 files changed, 24 insertions(+), 17 deletions(-) base-commit: f3e6330d7fe42b204af05a2dbc68b379e0ad179e -- 2.43.0