Historically all monitoring events have been associated with the L3
resource. This will change when support for telemetry events is added.

The RDT_RESOURCE_L3 resource carries a lot of state in the domain
structures which needs to be dealt with when a domain is taken offline
by removing the last CPU in the domain.

Refactor domain_remove_cpu_mon() so all the L3 processing is separated
from general actions of clearing the CPU bit in the mask and removing
directories from mon_data.

resctrl_offline_mon_domain() needs to remove domain specific
directories and files from the "mon_data" directories, but can skip the
L3 resource specific cleanup when called for other resource types.

Signed-off-by: Tony Luck <tony.luck@intel.com>
---
 arch/x86/kernel/cpu/resctrl/core.c | 17 +++++++++++------
 fs/resctrl/rdtgroup.c              |  5 ++++-
 2 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/resctrl/core.c b/arch/x86/kernel/cpu/resctrl/core.c
index 20b6f2bbf858..49e17c246c60 100644
--- a/arch/x86/kernel/cpu/resctrl/core.c
+++ b/arch/x86/kernel/cpu/resctrl/core.c
@@ -648,17 +648,22 @@ static void domain_remove_cpu_mon(int cpu, struct rdt_resource *r)
 	if (!domain_header_is_valid(hdr, RESCTRL_MON_DOMAIN, r->rid))
 		return;
 
-	d = container_of(hdr, struct rdt_mon_domain, hdr);
-	hw_dom = resctrl_to_arch_mon_dom(d);
+	cpumask_clear_cpu(cpu, &hdr->cpu_mask);
+	if (!cpumask_empty(&hdr->cpu_mask))
+		return;
 
-	cpumask_clear_cpu(cpu, &d->hdr.cpu_mask);
-	if (cpumask_empty(&d->hdr.cpu_mask)) {
+	switch (r->rid) {
+	case RDT_RESOURCE_L3:
+		d = container_of(hdr, struct rdt_mon_domain, hdr);
+		hw_dom = resctrl_to_arch_mon_dom(d);
 		resctrl_offline_mon_domain(r, d);
 		list_del_rcu(&d->hdr.list);
 		synchronize_rcu();
 		mon_domain_free(hw_dom);
-
-		return;
+		break;
+	default:
+		pr_warn_once("Unknown resource rid=%d\n", r->rid);
+		break;
 	}
 }
 
diff --git a/fs/resctrl/rdtgroup.c b/fs/resctrl/rdtgroup.c
index 77336d5e4915..05438e15e2ca 100644
--- a/fs/resctrl/rdtgroup.c
+++ b/fs/resctrl/rdtgroup.c
@@ -4047,6 +4047,9 @@ void resctrl_offline_mon_domain(struct rdt_resource *r, struct rdt_mon_domain *d
 	if (resctrl_mounted && resctrl_arch_mon_capable())
 		rmdir_mondata_subdir_allrdtgrp(r, d);
 
+	if (r->rid != RDT_RESOURCE_L3)
+		goto out_unlock;
+
 	if (resctrl_is_mbm_enabled())
 		cancel_delayed_work(&d->mbm_over);
 	if (resctrl_is_mon_event_enabled(QOS_L3_OCCUP_EVENT_ID) && has_busy_rmid(d)) {
@@ -4063,7 +4066,7 @@ void resctrl_offline_mon_domain(struct rdt_resource *r, struct rdt_mon_domain *d
 	}
 
 	domain_destroy_mon_state(d);
-
+out_unlock:
 	mutex_unlock(&rdtgroup_mutex);
 }
 
-- 
2.50.0

Hi Tony,

On 7/11/25 4:53 PM, Tony Luck wrote:
> Historically all monitoring events have been associated with the L3
> resource. This will change when support for telemetry events is added.

This is not "history" but the current state. How about:
"All monitoring events are associated with the L3 resource." 

Drop the "This will change when support for telemetry events is added." from the
first paragraph since it does not contribute to the context but can be used
in problem statement later. 

> 
> The RDT_RESOURCE_L3 resource carries a lot of state in the domain
> structures which needs to be dealt with when a domain is taken offline
> by removing the last CPU in the domain.

Above can be part of the context.

<insert problem statement here> 

> Refactor domain_remove_cpu_mon() so all the L3 processing is separated
> from general actions of clearing the CPU bit in the mask and removing
> directories from mon_data.

"directories from mon_data" -> "sub-directories from the mon_data directory"

> 
> resctrl_offline_mon_domain() needs to remove domain specific

"needs" -> "continues"

> directories and files from the "mon_data" directories, but can skip the
> L3 resource specific cleanup when called for other resource types.
> 
> Signed-off-by: Tony Luck <tony.luck@intel.com>
> ---

Patch looks good.

Reinette