Commit 2da20fd9 authored by Max Kellermann's avatar Max Kellermann Committed by Andrew Morton
Browse files

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

Expose a simple counter to userspace for monitoring tools.

(akpm: 2536c5c7 added the documentation but the code changes were lost)

Link: https://lkml.kernel.org/r/20250504180831.4190860-3-max.kellermann@ionos.com


Fixes: 2536c5c7 ("kernel/rcu/tree_stall: add /sys/kernel/rcu_stall_count")
Signed-off-by: default avatarMax 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: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 7266f590

kernel/rcu/tree_stall.h

+26 −0
Original line number Diff line number Diff line
@@ -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);