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kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count

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Expose a simple counter to userspace for monitoring tools.

(akpm: 2536c5c7d6 added the documentation but the code changes were lost)

Link: https://lkml.kernel.org/r/20250504180831.4190860-3-max.kellermann@ionos.com
Fixes: 2536c5c7d6 ("kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count")
Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Cc: Core Minyard <cminyard@mvista.com>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Joel Granados <joel.granados@kernel.org>
Cc: Max Kellermann <max.kellermann@ionos.com>
Cc: Song Liu <song@kernel.org>
Cc: Sourabh Jain <sourabhjain@linux.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Max Kellermann 2025-05-04 20:08:31 +02:00 committed by Andrew Morton
parent 7266f590ca
commit 2da20fd904
1 changed files with 26 additions and 0 deletions
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26
kernel/rcu/tree_stall.h
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@ -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);