From nobody Sun Sep 22 11:27:32 2024 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 45236C433EF for ; Sat, 12 Feb 2022 10:44:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233746AbiBLKoY (ORCPT ); Sat, 12 Feb 2022 05:44:24 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:43272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233619AbiBLKoG (ORCPT ); Sat, 12 Feb 2022 05:44:06 -0500 Received: from mailgw01.mediatek.com (unknown [60.244.123.138]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E51BB26573; Sat, 12 Feb 2022 02:43:58 -0800 (PST) X-UUID: 66f735713b934a70b748891a29852237-20220212 X-UUID: 66f735713b934a70b748891a29852237-20220212 Received: from mtkcas11.mediatek.inc [(172.21.101.40)] by mailgw01.mediatek.com (envelope-from ) (Generic MTA with TLSv1.2 ECDHE-RSA-AES256-SHA384 256/256) with ESMTP id 412303626; Sat, 12 Feb 2022 18:43:55 +0800 Received: from mtkexhb02.mediatek.inc (172.21.101.103) by mtkmbs07n2.mediatek.inc (172.21.101.141) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Sat, 12 Feb 2022 18:43:54 +0800 Received: from mtkcas10.mediatek.inc (172.21.101.39) by mtkexhb02.mediatek.inc (172.21.101.103) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Sat, 12 Feb 2022 18:43:54 +0800 Received: from mtksdccf07.mediatek.inc (172.21.84.99) by mtkcas10.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Sat, 12 Feb 2022 18:43:53 +0800 From: Lecopzer Chen To: CC: Catalin Marinas , Will Deacon , Mark Rutland , Peter Zijlstra , Ingo Molnar , Arnaldo Carvalho de Melo , Alexander Shishkin , Jiri Olsa , Namhyung Kim , , Matthias Brugger , "Marc Zyngier" , Julien Thierry , Kees Cook , Masahiro Yamada , Petr Mladek , Andrew Morton , Wang Qing , Luis Chamberlain , Xiaoming Ni , , , , , , , , Subject: [PATCH 4/5] kernel/watchdog: Adapt the watchdog_hld interface for async model Date: Sat, 12 Feb 2022 18:43:48 +0800 Message-ID: <20220212104349.14266-5-lecopzer.chen@mediatek.com> X-Mailer: git-send-email 2.18.0 In-Reply-To: <20220212104349.14266-1-lecopzer.chen@mediatek.com> References: <20220212104349.14266-1-lecopzer.chen@mediatek.com> MIME-Version: 1.0 X-MTK: N Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Pingfan Liu from: Pingfan Liu When lockup_detector_init()->watchdog_nmi_probe(), PMU may be not ready yet. E.g. on arm64, PMU is not ready until device_initcall(armv8_pmu_driver_init). And it is deeply integrated with the driver model and cpuhp. Hence it is hard to push this initialization before smp_init(). But it is easy to take an opposite approach by enabling watchdog_hld to get the capability of PMU async. The async model is achieved by expanding watchdog_nmi_probe() with -EBUSY, and a re-initializing work_struct which waits on a wait_queue_head. Signed-off-by: Pingfan Liu Co-developed-by: Lecopzer Chen Signed-off-by: Lecopzer Chen --- kernel/watchdog.c | 56 +++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 54 insertions(+), 2 deletions(-) diff --git a/kernel/watchdog.c b/kernel/watchdog.c index b71d434cf648..fa8490cfeef8 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -103,7 +103,11 @@ void __weak watchdog_nmi_disable(unsigned int cpu) hardlockup_detector_perf_disable(); } =20 -/* Return 0, if a NMI watchdog is available. Error code otherwise */ +/* + * Arch specific API. Return 0, if a NMI watchdog is available. -EBUSY if = not + * ready, and arch code should wake up hld_detector_wait when ready. Other + * negative value if not support. + */ int __weak __init watchdog_nmi_probe(void) { return hardlockup_detector_perf_init(); @@ -839,16 +843,64 @@ static void __init watchdog_sysctl_init(void) #define watchdog_sysctl_init() do { } while (0) #endif /* CONFIG_SYSCTL */ =20 +static void lockup_detector_delay_init(struct work_struct *work); +enum hld_detector_state detector_delay_init_state __initdata; + +struct wait_queue_head hld_detector_wait __initdata =3D + __WAIT_QUEUE_HEAD_INITIALIZER(hld_detector_wait); + +static struct work_struct detector_work __initdata =3D + __WORK_INITIALIZER(detector_work, lockup_detector_delay_init); + +static void __init lockup_detector_delay_init(struct work_struct *work) +{ + int ret; + + wait_event(hld_detector_wait, + detector_delay_init_state =3D=3D DELAY_INIT_READY); + ret =3D watchdog_nmi_probe(); + if (!ret) { + nmi_watchdog_available =3D true; + lockup_detector_setup(); + } else { + WARN_ON(ret =3D=3D -EBUSY); + pr_info("Perf NMI watchdog permanently disabled\n"); + } +} + +/* Ensure the check is called after the initialization of PMU driver */ +static int __init lockup_detector_check(void) +{ + if (detector_delay_init_state < DELAY_INIT_WAIT) + return 0; + + if (WARN_ON(detector_delay_init_state =3D=3D DELAY_INIT_WAIT)) { + detector_delay_init_state =3D DELAY_INIT_READY; + wake_up(&hld_detector_wait); + } + flush_work(&detector_work); + return 0; +} +late_initcall_sync(lockup_detector_check); + void __init lockup_detector_init(void) { + int ret; + if (tick_nohz_full_enabled()) pr_info("Disabling watchdog on nohz_full cores by default\n"); =20 cpumask_copy(&watchdog_cpumask, housekeeping_cpumask(HK_FLAG_TIMER)); =20 - if (!watchdog_nmi_probe()) + ret =3D watchdog_nmi_probe(); + if (!ret) nmi_watchdog_available =3D true; + else if (ret =3D=3D -EBUSY) { + detector_delay_init_state =3D DELAY_INIT_WAIT; + queue_work_on(smp_processor_id(), system_wq, &detector_work); + } + lockup_detector_setup(); watchdog_sysctl_init(); } --=20 2.25.1