2 files changed, 46 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index c186abed5c6d..8855481857b5 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1166,6 +1166,7 @@ static void __init init_uclamp(void)
                 uclamp_default[clamp_id] = uc_max;
 #ifdef CONFIG_UCLAMP_TASK_GROUP
                 root_task_group.uclamp_req[clamp_id] = uc_max;
+                root_task_group.uclamp[clamp_id] = uc_max;
 #endif
         }
 }
@@ -6824,6 +6825,7 @@ static inline void alloc_uclamp_sched_group(struct task_group *tg,
         for_each_clamp_id(clamp_id) {
                 uclamp_se_set(&tg->uclamp_req[clamp_id],
                               uclamp_none(clamp_id), false);
+                tg->uclamp[clamp_id] = parent->uclamp[clamp_id];
         }
 #endif
 }
@@ -7070,6 +7072,45 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
 }
 
 #ifdef CONFIG_UCLAMP_TASK_GROUP
+static void cpu_util_update_eff(struct cgroup_subsys_state *css)
+{
+        struct cgroup_subsys_state *top_css = css;
+        struct uclamp_se *uc_parent = NULL;
+        struct uclamp_se *uc_se = NULL;
+        unsigned int eff[UCLAMP_CNT];
+        unsigned int clamp_id;
+        unsigned int clamps;
+
+        css_for_each_descendant_pre(css, top_css) {
+                uc_parent = css_tg(css)->parent
+                        ? css_tg(css)->parent->uclamp : NULL;
+
+                for_each_clamp_id(clamp_id) {
+                        /* Assume effective clamps matches requested clamps */
+                        eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value;
+                        /* Cap effective clamps with parent's effective clamps */
+                        if (uc_parent &&
+                            eff[clamp_id] > uc_parent[clamp_id].value) {
+                                eff[clamp_id] = uc_parent[clamp_id].value;
+                        }
+                }
+                /* Ensure protection is always capped by limit */
+                eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]);
+
+                /* Propagate most restrictive effective clamps */
+                clamps = 0x0;
+                uc_se = css_tg(css)->uclamp;
+                for_each_clamp_id(clamp_id) {
+                        if (eff[clamp_id] == uc_se[clamp_id].value)
+                                continue;
+                        uc_se[clamp_id].value = eff[clamp_id];
+                        uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]);
+                        clamps |= (0x1 << clamp_id);
+                }
+                if (!clamps)
+                        css = css_rightmost_descendant(css);
+        }
+}
 
 /*
  * Integer 10^N with a given N exponent by casting to integer the literal "1eN"
@@ -7138,6 +7179,9 @@ static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf,
          */
         tg->uclamp_pct[clamp_id] = req.percent;
 
+        /* Update effective clamps to track the most restrictive value */
+        cpu_util_update_eff(of_css(of));
+
         rcu_read_unlock();
         mutex_unlock(&uclamp_mutex);
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index ae1be61fb279..5b343112a47b 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -397,6 +397,8 @@ struct task_group {
         unsigned int            uclamp_pct[UCLAMP_CNT];
         /* Clamp values requested for a task group */
         struct uclamp_se        uclamp_req[UCLAMP_CNT];
+        /* Effective clamp values used for a task group */
+        struct uclamp_se        uclamp[UCLAMP_CNT];
 #endif
 
 };