Merge branch 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull scheduler fixes from Thomas Gleixner:
 "Two fixes for the fair scheduling class:

   - Prevent freeing memory which is accessible by concurrent readers

   - Make the RCU annotations for numa groups consistent"

* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  sched/fair: Use RCU accessors consistently for ->numa_group
  sched/fair: Don't free p->numa_faults with concurrent readers

Author: torvalds

fs/exec.c

@@ -1828,7 +1828,7 @@ static int __do_execve_file(int fd, struct filename *filename,
 	membarrier_execve(current);
 	rseq_execve(current);
 	acct_update_integrals(current);
-	task_numa_free(current);
+	task_numa_free(current, false);
 	free_bprm(bprm);
 	kfree(pathbuf);
 	if (filename)

include/linux/sched.h

@@ -1092,7 +1092,15 @@ struct task_struct {
 	u64				last_sum_exec_runtime;
 	struct callback_head		numa_work;
 
-	struct numa_group		*numa_group;
+	/*
+	 * This pointer is only modified for current in syscall and
+	 * pagefault context (and for tasks being destroyed), so it can be read
+	 * from any of the following contexts:
+	 *  - RCU read-side critical section
+	 *  - current->numa_group from everywhere
+	 *  - task's runqueue locked, task not running
+	 */
+	struct numa_group __rcu		*numa_group;
 
 	/*
 	 * numa_faults is an array split into four regions:

include/linux/sched/numa_balancing.h

@@ -19,7 +19,7 @@
 extern void task_numa_fault(int last_node, int node, int pages, int flags);
 extern pid_t task_numa_group_id(struct task_struct *p);
 extern void set_numabalancing_state(bool enabled);
-extern void task_numa_free(struct task_struct *p);
+extern void task_numa_free(struct task_struct *p, bool final);
 extern bool should_numa_migrate_memory(struct task_struct *p, struct page *page,
 					int src_nid, int dst_cpu);
 #else
@@ -34,7 +34,7 @@ static inline pid_t task_numa_group_id(struct task_struct *p)
 static inline void set_numabalancing_state(bool enabled)
 {
 }
-static inline void task_numa_free(struct task_struct *p)
+static inline void task_numa_free(struct task_struct *p, bool final)
 {
 }
 static inline bool should_numa_migrate_memory(struct task_struct *p,

kernel/fork.c

@@ -726,7 +726,7 @@ void __put_task_struct(struct task_struct *tsk)
 	WARN_ON(tsk == current);
 
 	cgroup_free(tsk);
-	task_numa_free(tsk);
+	task_numa_free(tsk, true);
 	security_task_free(tsk);
 	exit_creds(tsk);
 	delayacct_tsk_free(tsk);