From 2da20fd904f87f7bb31b79719bc3dda4093f8cdb Mon Sep 17 00:00:00 2001 From: Max Kellermann Date: Sun, 4 May 2025 20:08:31 +0200 Subject: [PATCH] kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count Expose a simple counter to userspace for monitoring tools. (akpm: 2536c5c7d6ae added the documentation but the code changes were lost) Link: https://lkml.kernel.org/r/20250504180831.4190860-3-max.kellermann@ionos.com Fixes: 2536c5c7d6ae ("kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count") Signed-off-by: Max Kellermann Cc: Core Minyard Cc: Doug Anderson Cc: Joel Granados Cc: Max Kellermann Cc: Song Liu Cc: Sourabh Jain Signed-off-by: Andrew Morton --- kernel/rcu/tree_stall.h | 26 ++++++++++++++++++++++++++ 1 file changed, 26 insertions(+) diff --git a/kernel/rcu/tree_stall.h b/kernel/rcu/tree_stall.h index 56b21219442b6..486c00536207d 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; +#ifdef CONFIG_SYSFS + +static unsigned int rcu_stall_count; + +static ssize_t rcu_stall_count_show(struct kobject *kobj, struct kobj_attribute *attr, + char *page) +{ + return sysfs_emit(page, "%u\n", rcu_stall_count); +} + +static struct kobj_attribute rcu_stall_count_attr = __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; +#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 stuck CSD-lock.\n", rcu_state.name); -- 2.39.5