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Mon, 16 Feb 2026 18:50:09 +0000 (GMT) From: Aboorva Devarajan To: rafael@kernel.org, christian.loehle@arm.com, daniel.lezcano@linaro.org Cc: aboorvad@linux.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/4] cpuidle: Skip governor when only one idle state is available Date: Tue, 17 Feb 2026 00:20:02 +0530 Message-ID: <20260216185005.1131593-2-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260216185005.1131593-1-aboorvad@linux.ibm.com> References: <20260216185005.1131593-1-aboorvad@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-Proofpoint-ORIG-GUID: cgjSCwj_JlpQ_F2rxlQ_Uu3i7FrMgG5D X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjE2MDE1OSBTYWx0ZWRfX/B8qU2BL2fTM Om0WQO+BHNAaz0TwglnBiF8yRGHaa+qfo/uGrEvbuaMMl+ClCBOVtw7qIdDDmtvgJsCMWt/a2iG n9zzA+CAkJHyGBOBiHcdId2ftjAL4rFjKIQRDFbUzFuNWErwp4yn4mxxnRuoJ7NBIsLjgfqhVMG nmQQPbogC7cyAt3nMJOHBOqCC/DeWFvTmypy0fmX178Smzq17RMICIFxha3jAhBM/jBxg9QG6ME WVYIEDbBIReGLHiok+ZbVYB6gsoelWt9PoPuOQlg8H/jCa0rdXpYmcfblqrsx0rJEIPpNfImHEj DV8ZoogX/WDSq5UFdFCXlsr2HUZ7T98HmHi2yyS7rV3GDcoSvEZ+gFiyJE9j05eDwT8JgeV81oB dMYyzplTaaCysqy/kChVsiqeA2zvZAi359fIXTmb8AVoU5dAD27RYz6X+wljmqd/htfQWvjBukw JfhF6xWjGUs44jKoGkA== X-Proofpoint-GUID: cgjSCwj_JlpQ_F2rxlQ_Uu3i7FrMgG5D X-Authority-Analysis: v=2.4 cv=U+mfzOru c=1 sm=1 tr=0 ts=699366e6 cx=c_pps a=GFwsV6G8L6GxiO2Y/PsHdQ==:117 a=GFwsV6G8L6GxiO2Y/PsHdQ==:17 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=VnNF1IyMAAAA:8 a=YIsf0ydp8jgAjUZD7Z8A:9 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-16_06,2026-02-16_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 impostorscore=0 malwarescore=0 spamscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602160159 Content-Type: text/plain; charset="utf-8" On certain platforms (PowerNV systems without a power-mgt DT node), cpuidle may register only a single idle state. In cases where that single state is a polling state (state 0), the ladder governor may incorrectly treat state 1 as the first usable state and pass an out-of-bounds index. This can lead to a NULL enter callback being invoked, ultimately resulting in a system crash. [ 13.342636] cpuidle-powernv : Only Snooze is available [ 13.351854] Faulting instruction address: 0x00000000 [ 13.376489] NIP [0000000000000000] 0x0 [ 13.378351] LR [c000000001e01974] cpuidle_enter_state+0x2c4/0x668 Fix this by adding a bail-out in cpuidle_select() that returns state 0 directly when state_count <=3D 1, bypassing the governor and keeping the tick running. Fixes: dc2251bf98c6 ("cpuidle: Eliminate the CPUIDLE_DRIVER_STATE_START sym= bol") Signed-off-by: Aboorva Devarajan Reviewed-by: Christian Loehle --- drivers/cpuidle/cpuidle.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff --git a/drivers/cpuidle/cpuidle.c b/drivers/cpuidle/cpuidle.c index c7876e9e024f..65fbb8e807b9 100644 --- a/drivers/cpuidle/cpuidle.c +++ b/drivers/cpuidle/cpuidle.c @@ -359,6 +359,16 @@ noinstr int cpuidle_enter_state(struct cpuidle_device = *dev, int cpuidle_select(struct cpuidle_driver *drv, struct cpuidle_device *dev, bool *stop_tick) { + /* + * If there is only a single idle state (or none), there is nothing + * meaningful for the governor to choose. Skip the governor and + * always use state 0 with the tick running. + */ + if (drv->state_count <=3D 1) { + *stop_tick =3D false; + return 0; + } + return cpuidle_curr_governor->select(drv, dev, stop_tick); } =20 --=20 2.52.0 From nobody Thu Mar 5 06:32:15 2026 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8EDD52E7F25; Mon, 16 Feb 2026 18:50:28 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.163.158.5 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771267829; cv=none; b=KhFq2Y3fr8vYss/LzCB7JvPcCHAgCwLdcF2p3dzt7GKO+L0wW76CyoJco8Xp+6yygXvegTiqwEv9zyf0sYLqHfIdQH79pmytZSLc3denpoFw3N1qKgkWzeVthBiUkrRhJJ34sP4A+CzA6xzTiDp42ecJoX2z/cwM/OBO52up8j8= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1771267829; 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charset="utf-8" cpuidle systems where the governor has no choice because there's only a single idle state are now handled by cpuidle core and bypass the governor, so remove the related handling. Signed-off-by: Aboorva Devarajan Reviewed-by: Christian Loehle --- drivers/cpuidle/governors/haltpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/governors/haltpoll.c b/drivers/cpuidle/governo= rs/haltpoll.c index 663b7f164d20..ed3952df8526 100644 --- a/drivers/cpuidle/governors/haltpoll.c +++ b/drivers/cpuidle/governors/haltpoll.c @@ -52,7 +52,7 @@ static int haltpoll_select(struct cpuidle_driver *drv, { s64 latency_req =3D cpuidle_governor_latency_req(dev->cpu); =20 - if (!drv->state_count || latency_req =3D=3D 0) { + if (latency_req =3D=3D 0) { *stop_tick =3D false; return 0; } --=20 2.52.0 From nobody Thu Mar 5 06:32:15 2026 Received: from mx0a-001b2d01.pphosted.com (mx0a-001b2d01.pphosted.com [148.163.156.1]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id AD0A42E7F3E; Mon, 16 Feb 2026 18:50:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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charset="utf-8" From: Christian Loehle cpuidle systems where the governor has no choice because there's only a single idle state are now handled by cpuidle core and bypass the governor, so remove the related handling. Signed-off-by: Christian Loehle --- drivers/cpuidle/governors/teo.c | 6 ------ 1 file changed, 6 deletions(-) diff --git a/drivers/cpuidle/governors/teo.c b/drivers/cpuidle/governors/te= o.c index 81ac5fd58a1c..9b5b8c617806 100644 --- a/drivers/cpuidle/governors/teo.c +++ b/drivers/cpuidle/governors/teo.c @@ -317,12 +317,6 @@ static int teo_select(struct cpuidle_driver *drv, stru= ct cpuidle_device *dev, */ cpu_data->sleep_length_ns =3D KTIME_MAX; =20 - /* Check if there is any choice in the first place. */ - if (drv->state_count < 2) { - idx =3D 0; - goto out_tick; - } - if (!dev->states_usage[0].disable) idx =3D 0; =20 --=20 2.52.0 From nobody Thu Mar 5 06:32:15 2026 Received: from mx0b-001b2d01.pphosted.com (mx0b-001b2d01.pphosted.com [148.163.158.5]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A0CF029AAF7; Mon, 16 Feb 2026 18:50:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Mon, 16 Feb 2026 18:50:17 +0000 (GMT) From: Aboorva Devarajan To: rafael@kernel.org, christian.loehle@arm.com, daniel.lezcano@linaro.org Cc: aboorvad@linux.ibm.com, linux-pm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 4/4] cpuidle: menu: Remove single state handling Date: Tue, 17 Feb 2026 00:20:05 +0530 Message-ID: <20260216185005.1131593-5-aboorvad@linux.ibm.com> X-Mailer: git-send-email 2.52.0 In-Reply-To: <20260216185005.1131593-1-aboorvad@linux.ibm.com> References: <20260216185005.1131593-1-aboorvad@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-Proofpoint-ORIG-GUID: jZLpsB_5-pUAzWO5SAsd3RIpFEycbCD- X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwMjE2MDE1OSBTYWx0ZWRfX5WR7W/2yvzXu gTSGA6DNo0ZsdIF+IUSlyL5UXOk/vCTwsHyGD2Per6K4DY29JKmwjBoFyAi79xNkouuyz3JRwzs pT8fH889Dn/nlwXOzhYVfUSkh8JcWydPyQmr99W4Ab9rALyXvFJnFfTyQm3E5JiAK39g2sTrq8I yC08dC+9+/CozrWOLlfJBXYREdabj2nxY4Y00xieQENWof6kaKZUD+qWZlXu7O3G7jZOJMrsgqz 5eGdCummpo9OW3Kq0YLYxVFoI7CMozGe+ajI+yorTw34aTxtNpl+HCgt7K1W1u6DGkH1GYpxGw4 oLvf/q6yZNBxwED8L1/U5jjpGCz0Qs+9ffjvwbCG/tx2DdohSgdHjsLaIrAOOEsKLaGW7LfNKTm oo//VvMd0tXvMkasMugEbz50kUEHhhmDNlh74ziZVsMtCnQlgkC2s/4y27M9/dPIJvP3aaxHfka lQR/tU85ouvqTlJ/Bng== X-Proofpoint-GUID: jZLpsB_5-pUAzWO5SAsd3RIpFEycbCD- X-Authority-Analysis: v=2.4 cv=U+mfzOru c=1 sm=1 tr=0 ts=699366ed cx=c_pps a=3Bg1Hr4SwmMryq2xdFQyZA==:117 a=3Bg1Hr4SwmMryq2xdFQyZA==:17 a=HzLeVaNsDn8A:10 a=VkNPw1HP01LnGYTKEx00:22 a=Mpw57Om8IfrbqaoTuvik:22 a=GgsMoib0sEa3-_RKJdDe:22 a=7CQSdrXTAAAA:8 a=H2bq5lvY-VcIl05QleYA:9 a=a-qgeE7W1pNrGK8U0ZQC:22 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-02-16_06,2026-02-16_04,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 bulkscore=0 impostorscore=0 malwarescore=0 spamscore=0 adultscore=0 phishscore=0 lowpriorityscore=0 priorityscore=1501 suspectscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.22.0-2601150000 definitions=main-2602160159 Content-Type: text/plain; charset="utf-8" From: Christian Loehle cpuidle systems where the governor has no choice because there's only a single idle state are now handled by cpuidle core and bypass the governor, so remove the related handling. Signed-off-by: Christian Loehle --- drivers/cpuidle/governors/menu.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/cpuidle/governors/menu.c b/drivers/cpuidle/governors/m= enu.c index 64d6f7a1c776..fdfa5d7e10a6 100644 --- a/drivers/cpuidle/governors/menu.c +++ b/drivers/cpuidle/governors/menu.c @@ -271,7 +271,7 @@ static int menu_select(struct cpuidle_driver *drv, stru= ct cpuidle_device *dev, data->bucket =3D BUCKETS - 1; } =20 - if (unlikely(drv->state_count <=3D 1 || latency_req =3D=3D 0) || + if (unlikely(latency_req =3D=3D 0) || ((data->next_timer_ns < drv->states[1].target_residency_ns || latency_req < drv->states[1].exit_latency_ns) && !dev->states_usage[0].disable)) { --=20 2.52.0