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[2003:dc:6f46:c100:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5fa77b914b4sm4077440a12.51.2025.05.04.11.08.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 May 2025 11:08:36 -0700 (PDT) From: Max Kellermann To: akpm@linux-foundation.org, song@kernel.org, joel.granados@kernel.org, dianders@chromium.org, cminyard@mvista.com, linux-kernel@vger.kernel.org Cc: Max Kellermann Subject: [PATCH v2 1/2] kernel/watchdog: add /sys/kernel/{hard,soft}lockup_count Date: Sun, 4 May 2025 20:08:30 +0200 Message-ID: <20250504180831.4190860-2-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250504180831.4190860-1-max.kellermann@ionos.com> References: <20250504180831.4190860-1-max.kellermann@ionos.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 Content-Type: text/plain; charset="utf-8" There is /proc/sys/kernel/hung_task_detect_count, /sys/kernel/warn_count and /sys/kernel/oops_count but there is no userspace-accessible counter for hard/soft lockups. Having this is useful for monitoring tools. Signed-off-by: Max Kellermann --- v1 -> v2: added documentation; added patch set cover letter with justification --- .../ABI/testing/sysfs-kernel-hardlockup_count | 7 +++ .../ABI/testing/sysfs-kernel-softlockup_count | 7 +++ kernel/watchdog.c | 53 +++++++++++++++++++ 3 files changed, 67 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-kernel-hardlockup_count create mode 100644 Documentation/ABI/testing/sysfs-kernel-softlockup_count diff --git a/Documentation/ABI/testing/sysfs-kernel-hardlockup_count b/Docu= mentation/ABI/testing/sysfs-kernel-hardlockup_count new file mode 100644 index 000000000000..dfdd4078b077 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-hardlockup_count @@ -0,0 +1,7 @@ +What: /sys/kernel/hardlockup_count +Date: May 2025 +KernelVersion: 6.16 +Contact: Linux kernel mailing list +Description: + Shows how many times the system has detected a hard lockup since last bo= ot. + Available only if CONFIG_HARDLOCKUP_DETECTOR is enabled. diff --git a/Documentation/ABI/testing/sysfs-kernel-softlockup_count b/Docu= mentation/ABI/testing/sysfs-kernel-softlockup_count new file mode 100644 index 000000000000..337ff5531b5f --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-softlockup_count @@ -0,0 +1,7 @@ +What: /sys/kernel/softlockup_count +Date: May 2025 +KernelVersion: 6.16 +Contact: Linux kernel mailing list +Description: + Shows how many times the system has detected a soft lockup since last bo= ot. + Available only if CONFIG_SOFTLOCKUP_DETECTOR is enabled. diff --git a/kernel/watchdog.c b/kernel/watchdog.c index 9fa2af9dbf2c..09994bfb47af 100644 --- a/kernel/watchdog.c +++ b/kernel/watchdog.c @@ -63,6 +63,29 @@ int __read_mostly sysctl_hardlockup_all_cpu_backtrace; */ unsigned int __read_mostly hardlockup_panic =3D IS_ENABLED(CONFIG_BOOTPARAM_HARDLOCKUP_PANIC); + +#ifdef CONFIG_SYSFS + +static unsigned int hardlockup_count; + +static ssize_t hardlockup_count_show(struct kobject *kobj, struct kobj_att= ribute *attr, + char *page) +{ + return sysfs_emit(page, "%u\n", hardlockup_count); +} + +static struct kobj_attribute hardlockup_count_attr =3D __ATTR_RO(hardlocku= p_count); + +static __init int kernel_hardlockup_sysfs_init(void) +{ + sysfs_add_file_to_group(kernel_kobj, &hardlockup_count_attr.attr, NULL); + return 0; +} + +late_initcall(kernel_hardlockup_sysfs_init); + +#endif // CONFIG_SYSFS + /* * We may not want to enable hard lockup detection by default in all cases, * for example when running the kernel as a guest on a hypervisor. In these @@ -169,6 +192,10 @@ void watchdog_hardlockup_check(unsigned int cpu, struc= t pt_regs *regs) unsigned int this_cpu =3D smp_processor_id(); unsigned long flags; =20 +#ifdef CONFIG_SYSFS + ++hardlockup_count; +#endif + /* Only print hardlockups once. */ if (per_cpu(watchdog_hardlockup_warned, cpu)) return; @@ -311,6 +338,28 @@ unsigned int __read_mostly softlockup_panic =3D static bool softlockup_initialized __read_mostly; static u64 __read_mostly sample_period; =20 +#ifdef CONFIG_SYSFS + +static unsigned int softlockup_count; + +static ssize_t softlockup_count_show(struct kobject *kobj, struct kobj_att= ribute *attr, + char *page) +{ + return sysfs_emit(page, "%u\n", softlockup_count); +} + +static struct kobj_attribute softlockup_count_attr =3D __ATTR_RO(softlocku= p_count); + +static __init int kernel_softlockup_sysfs_init(void) +{ + sysfs_add_file_to_group(kernel_kobj, &softlockup_count_attr.attr, NULL); + return 0; +} + +late_initcall(kernel_softlockup_sysfs_init); + +#endif // CONFIG_SYSFS + /* Timestamp taken after the last successful reschedule. */ static DEFINE_PER_CPU(unsigned long, watchdog_touch_ts); /* Timestamp of the last softlockup report. */ @@ -742,6 +791,10 @@ static enum hrtimer_restart watchdog_timer_fn(struct h= rtimer *hrtimer) touch_ts =3D __this_cpu_read(watchdog_touch_ts); duration =3D is_softlockup(touch_ts, period_ts, now); if (unlikely(duration)) { +#ifdef CONFIG_SYSFS + ++softlockup_count; +#endif + /* * Prevent multiple soft-lockup reports if one cpu is already * engaged in dumping all cpu back traces. --=20 2.47.2 From nobody Sun Feb 8 15:58:42 2026 Received: from mail-ed1-f49.google.com (mail-ed1-f49.google.com [209.85.208.49]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 86D561991CB for ; Sun, 4 May 2025 18:08:39 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.208.49 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746382121; cv=none; b=Gw6jByn85DY/rMlMjLprb6P0iny12PP9GfB8gcmmbn2erJ4vQkxeM7x5UWbA9KFZ8e6fwe/ACv/zVxN25CdsLVbJ1YxIjl8BFqKIni036pcN0+vnSqcDSEas4P8ynX2qiLCx7YUmKmDrcWJt7jsNgbSSsBZh/0VC6IRM7a6JHFo= ARC-Message-Signature: i=1; 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[2003:dc:6f46:c100:230:64ff:fe74:809]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5fa77b914b4sm4077440a12.51.2025.05.04.11.08.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 04 May 2025 11:08:37 -0700 (PDT) From: Max Kellermann To: akpm@linux-foundation.org, song@kernel.org, joel.granados@kernel.org, dianders@chromium.org, cminyard@mvista.com, linux-kernel@vger.kernel.org Cc: Max Kellermann Subject: [PATCH v2 2/2] kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count Date: Sun, 4 May 2025 20:08:31 +0200 Message-ID: <20250504180831.4190860-3-max.kellermann@ionos.com> X-Mailer: git-send-email 2.47.2 In-Reply-To: <20250504180831.4190860-1-max.kellermann@ionos.com> References: <20250504180831.4190860-1-max.kellermann@ionos.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 Content-Type: text/plain; charset="utf-8" Exposing a simple counter to userspace for monitoring tools. Signed-off-by: Max Kellermann --- v1 -> v2: added documentation --- .../ABI/testing/sysfs-kernel-rcu_stall_count | 6 +++++ kernel/rcu/tree_stall.h | 26 +++++++++++++++++++ 2 files changed, 32 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-kernel-rcu_stall_count diff --git a/Documentation/ABI/testing/sysfs-kernel-rcu_stall_count b/Docum= entation/ABI/testing/sysfs-kernel-rcu_stall_count new file mode 100644 index 000000000000..a4a97a7f4a4d --- /dev/null +++ b/Documentation/ABI/testing/sysfs-kernel-rcu_stall_count @@ -0,0 +1,6 @@ +What: /sys/kernel/rcu_stall_count +Date: May 2025 +KernelVersion: 6.16 +Contact: Linux kernel mailing list +Description: + Shows how many times the system has detected an RCU stall since last boo= t. diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 925fcdad5dea..158330524795 100644 --- a/kernel/rcu/tree_stall.h +++ b/kernel/rcu/tree_stall.h @@ -20,6 +20,28 @@ int sysctl_panic_on_rcu_stall __read_mostly; int sysctl_max_rcu_stall_to_panic __read_mostly; =20 +#ifdef CONFIG_SYSFS + +static unsigned int rcu_stall_count; + +static ssize_t rcu_stall_count_show(struct kobject *kobj, struct kobj_attr= ibute *attr, + char *page) +{ + return sysfs_emit(page, "%u\n", rcu_stall_count); +} + +static struct kobj_attribute rcu_stall_count_attr =3D __ATTR_RO(rcu_stall_= count); + +static __init int kernel_rcu_stall_sysfs_init(void) +{ + sysfs_add_file_to_group(kernel_kobj, &rcu_stall_count_attr.attr, NULL); + return 0; +} + +late_initcall(kernel_rcu_stall_sysfs_init); + +#endif // CONFIG_SYSFS + #ifdef CONFIG_PROVE_RCU #define RCU_STALL_DELAY_DELTA (5 * HZ) #else @@ -784,6 +806,10 @@ static void check_cpu_stall(struct rcu_data *rdp) if (kvm_check_and_clear_guest_paused()) return; =20 +#ifdef CONFIG_SYSFS + ++rcu_stall_count; +#endif + rcu_stall_notifier_call_chain(RCU_STALL_NOTIFY_NORM, (void *)j - gps); if (READ_ONCE(csd_lock_suppress_rcu_stall) && csd_lock_is_stuck()) { pr_err("INFO: %s detected stall, but suppressed full report due to a st= uck CSD-lock.\n", rcu_state.name); --=20 2.47.2