Merge tag 'sched-urgent-2026-09-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Ingo Molnar:

 - Fix LLC mis-scheduling bugs (Tim Chen, Lu Wang)

 - Fix cache-grouping related scheduling statistics UAF bugs (Tim Chen)

 - Skip kernel threads for cache aware scheduling to rubustify the code
   (Chen Yu)

 - Refresh LLC capacity across CPU hotplug, to fix capacity
   underestimation bug (Davi Chaves Azevedo)

 - Account PSI IRQ time to the execution context, not the scheduling
   context, to fix proxy scheduling accounting bug (Zhan Xusheng)

* tag 'sched-urgent-2026-09-27' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/core: Account PSI IRQ time to the execution context, not the scheduling context
  sched/cache: Refresh LLC capacity across CPU hotplug, to fix capacity underestimation bug
  sched/cache: Skip kernel threads for cache aware scheduling to rubustify the code
  sched/cache: Introduce task_struct->sched_cache_grp to fix UAF
  sched/cache: Decouple sched_cache_group from mm to fix UAF
  sched/cache: Honor migrate_llc_task semantics in active load balance, to fix LLC mis-scheduling bug
  sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug

3 files changed, 25 insertions, 14 deletions

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 6d815f6440c9..f3e5a2fadbe5 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -1226,7 +1226,7 @@ struct mm_struct {
 		struct mm_mm_cid mm_cid;
 
 		/* sched_cache related statistics */
-		struct sched_cache_stat sc_stat;
+		struct sched_cache_group *sched_cache_grp;
 #ifdef CONFIG_MMU
 		atomic_long_t pgtables_bytes;	/* size of all page tables */
 #endif
@@ -1624,8 +1624,9 @@ static inline unsigned int mm_cid_size(void)
 #endif /* CONFIG_SCHED_MM_CID */
 
 #ifdef CONFIG_SCHED_CACHE
-void mm_init_sched(struct mm_struct *mm,
-		   struct sched_cache_time __percpu *pcpu_sched);
+int mm_init_sched(struct mm_struct *mm,
+		  struct sched_cache_time __percpu *pcpu_sched);
+void mm_destroy_sched(struct mm_struct *mm);
 
 static inline int mm_alloc_sched_noprof(struct mm_struct *mm)
 {
@@ -1635,17 +1636,11 @@ static inline int mm_alloc_sched_noprof(struct mm_struct *mm)
 	if (!pcpu_sched)
 		return -ENOMEM;
 
-	mm_init_sched(mm, pcpu_sched);
-	return 0;
+	return mm_init_sched(mm, pcpu_sched);
 }
 
 #define mm_alloc_sched(...)	alloc_hooks(mm_alloc_sched_noprof(__VA_ARGS__))
 
-static inline void mm_destroy_sched(struct mm_struct *mm)
-{
-	free_percpu(mm->sc_stat.pcpu_sched);
-	mm->sc_stat.pcpu_sched = NULL;
-}
 #else /* !CONFIG_SCHED_CACHE */
 
 static inline int mm_alloc_sched(struct mm_struct *mm) { return 0; }
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 705970d07614..d35ae49a991f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1433,6 +1433,7 @@ struct task_struct {
 
 #ifdef CONFIG_SCHED_CACHE
 	struct callback_head		cache_work;
+	struct sched_cache_group __rcu	*sched_cache_grp;
 	int				preferred_llc;
 	/* 1: task was enqueued to its preferred LLC, 0 otherwise */
 	int				pref_llc_queued;
@@ -2405,7 +2406,7 @@ struct sched_cache_time {
 	unsigned long epoch;
 };
 
-struct sched_cache_stat {
+struct sched_cache_group {
 	struct sched_cache_time __percpu *pcpu_sched;
 	raw_spinlock_t lock;
 	unsigned long epoch;
@@ -2413,11 +2414,26 @@ struct sched_cache_stat {
 	unsigned long next_scan;
 	unsigned long footprint;
 	int cpu;
+	refcount_t refcnt;
+	struct rcu_head rcu;
 } ____cacheline_aligned_in_smp;
 
+struct sched_cache_group *sched_cache_group_get(struct sched_cache_group *grp);
+struct sched_cache_group *task_cache_group_get(struct task_struct *p);
+
+void sched_cache_fork(struct task_struct *p);
+void sched_cache_fork_cleanup(struct task_struct *p);
+void sched_cache_exec_mmap(struct task_struct *p, struct mm_struct *mm);
+void sched_cache_exit_mm(struct task_struct *p);
+
 #else
 
-struct sched_cache_stat { };
+struct sched_cache_group { };
+
+static inline void sched_cache_fork(struct task_struct *p) { }
+static inline void sched_cache_fork_cleanup(struct task_struct *p) { }
+static inline void sched_cache_exec_mmap(struct task_struct *p, struct mm_struct *mm) { }
+static inline void sched_cache_exit_mm(struct task_struct *p) { }
 
 #endif
 
diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
index b5d9d7c2b8ad..f96812d71c51 100644
--- a/include/linux/sched/topology.h
+++ b/include/linux/sched/topology.h
@@ -281,9 +281,9 @@ static inline int task_node(const struct task_struct *p)
 }
 
 #ifdef CONFIG_SCHED_CACHE
-extern void sched_update_llc_bytes(unsigned int cpu);
+extern void sched_update_llc_bytes(const struct cpumask *cpus);
 #else
-static inline void sched_update_llc_bytes(unsigned int cpu) { }
+static inline void sched_update_llc_bytes(const struct cpumask *cpus) { }
 #endif
 
 #endif /* _LINUX_SCHED_TOPOLOGY_H */