1 files changed, 47 insertions, 0 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 44999505e1bf..240157c13ddc 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2951,6 +2951,47 @@ asmlinkage __visible void __sched notrace preempt_schedule(void)
 }
 NOKPROBE_SYMBOL(preempt_schedule);
 EXPORT_SYMBOL(preempt_schedule);
+
+#ifdef CONFIG_CONTEXT_TRACKING
+/**
+ * preempt_schedule_context - preempt_schedule called by tracing
+ *
+ * The tracing infrastructure uses preempt_enable_notrace to prevent
+ * recursion and tracing preempt enabling caused by the tracing
+ * infrastructure itself. But as tracing can happen in areas coming
+ * from userspace or just about to enter userspace, a preempt enable
+ * can occur before user_exit() is called. This will cause the scheduler
+ * to be called when the system is still in usermode.
+ *
+ * To prevent this, the preempt_enable_notrace will use this function
+ * instead of preempt_schedule() to exit user context if needed before
+ * calling the scheduler.
+ */
+asmlinkage __visible void __sched notrace preempt_schedule_context(void)
+{
+        enum ctx_state prev_ctx;
+
+        if (likely(!preemptible()))
+                return;
+
+        do {
+                __preempt_count_add(PREEMPT_ACTIVE);
+                /*
+                 * Needs preempt disabled in case user_exit() is traced
+                 * and the tracer calls preempt_enable_notrace() causing
+                 * an infinite recursion.
+                 */
+                prev_ctx = exception_enter();
+                __schedule();
+                exception_exit(prev_ctx);
+
+                __preempt_count_sub(PREEMPT_ACTIVE);
+                barrier();
+        } while (need_resched());
+}
+EXPORT_SYMBOL_GPL(preempt_schedule_context);
+#endif /* CONFIG_CONTEXT_TRACKING */
+
 #endif /* CONFIG_PREEMPT */
 
 /*
@@ -7833,6 +7874,11 @@ static void cpu_cgroup_css_offline(struct cgroup_subsys_state *css)
         sched_offline_group(tg);
 }
 
+static void cpu_cgroup_fork(struct task_struct *task)
+{
+        sched_move_task(task);
+}
+
 static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css,
                                  struct cgroup_taskset *tset)
 {
@@ -8205,6 +8251,7 @@ struct cgroup_subsys cpu_cgrp_subsys = {
         .css_free       = cpu_cgroup_css_free,
         .css_online     = cpu_cgroup_css_online,
         .css_offline    = cpu_cgroup_css_offline,
+        .fork           = cpu_cgroup_fork,
         .can_attach     = cpu_cgroup_can_attach,
         .attach         = cpu_cgroup_attach,
         .exit           = cpu_cgroup_exit,