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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