7 files changed, 99 insertions, 56 deletions

diff --git a/arch/x86/include/asm/preempt.h b/arch/x86/include/asm/preempt.h
index 7024c12f7bfe..400873450e33 100644
--- a/arch/x86/include/asm/preempt.h
+++ b/arch/x86/include/asm/preempt.h
@@ -105,6 +105,7 @@ static __always_inline bool should_resched(void)
 # ifdef CONFIG_CONTEXT_TRACKING
     extern asmlinkage void ___preempt_schedule_context(void);
 #   define __preempt_schedule_context() asm ("call ___preempt_schedule_context")
+    extern asmlinkage void preempt_schedule_context(void);
 # endif
 #endif
 
diff --git a/include/uapi/linux/sched.h b/include/uapi/linux/sched.h
index 34f9d7387d13..b932be9f5c5b 100644
--- a/include/uapi/linux/sched.h
+++ b/include/uapi/linux/sched.h
@@ -13,7 +13,7 @@
 #define CLONE_VFORK     0x00004000      /* set if the parent wants the child to wake it up on mm_release */
 #define CLONE_PARENT    0x00008000      /* set if we want to have the same parent as the cloner */
 #define CLONE_THREAD    0x00010000      /* Same thread group? */
-#define CLONE_NEWNS     0x00020000      /* New namespace group? */
+#define CLONE_NEWNS     0x00020000      /* New mount namespace group */
 #define CLONE_SYSVSEM   0x00040000      /* share system V SEM_UNDO semantics */
 #define CLONE_SETTLS    0x00080000      /* create a new TLS for the child */
 #define CLONE_PARENT_SETTID     0x00100000      /* set the TID in the parent */
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index 5664985c46a0..937ecdfdf258 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -107,46 +107,6 @@ void context_tracking_user_enter(void)
 }
 NOKPROBE_SYMBOL(context_tracking_user_enter);
 
-#ifdef CONFIG_PREEMPT
-/**
- * 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;
-
-        /*
-         * Need to disable preemption in case user_exit() is traced
-         * and the tracer calls preempt_enable_notrace() causing
-         * an infinite recursion.
-         */
-        preempt_disable_notrace();
-        prev_ctx = exception_enter();
-        preempt_enable_no_resched_notrace();
-
-        preempt_schedule();
-
-        preempt_disable_notrace();
-        exception_exit(prev_ctx);
-        preempt_enable_notrace();
-}
-EXPORT_SYMBOL_GPL(preempt_schedule_context);
-#endif /* CONFIG_PREEMPT */
-
 /**
  * context_tracking_user_exit - Inform the context tracking that the CPU is
  *                              exiting userspace mode and entering the kernel.
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,
diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 256e577faf1b..5285332392d5 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -518,12 +518,20 @@ again:
         }
 
         /*
-         * We need to take care of a possible races here. In fact, the
-         * task might have changed its scheduling policy to something
-         * different from SCHED_DEADLINE or changed its reservation
-         * parameters (through sched_setattr()).
+         * We need to take care of several possible races here:
+         *
+         *   - the task might have changed its scheduling policy
+         *     to something different than SCHED_DEADLINE
+         *   - the task might have changed its reservation parameters
+         *     (through sched_setattr())
+         *   - the task might have been boosted by someone else and
+         *     might be in the boosting/deboosting path
+         *
+         * In all this cases we bail out, as the task is already
+         * in the runqueue or is going to be enqueued back anyway.
          */
-        if (!dl_task(p) || dl_se->dl_new)
+        if (!dl_task(p) || dl_se->dl_new ||
+            dl_se->dl_boosted || !dl_se->dl_throttled)
                 goto unlock;
 
         sched_clock_tick();
@@ -532,7 +540,7 @@ again:
         dl_se->dl_yielded = 0;
         if (task_on_rq_queued(p)) {
                 enqueue_task_dl(rq, p, ENQUEUE_REPLENISH);
-                if (task_has_dl_policy(rq->curr))
+                if (dl_task(rq->curr))
                         check_preempt_curr_dl(rq, p, 0);
                 else
                         resched_curr(rq);
@@ -847,8 +855,19 @@ static void enqueue_task_dl(struct rq *rq, struct task_struct *p, int flags)
          * smaller than our one... OTW we keep our runtime and
          * deadline.
          */
-        if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio))
+        if (pi_task && p->dl.dl_boosted && dl_prio(pi_task->normal_prio)) {
                 pi_se = &pi_task->dl;
+        } else if (!dl_prio(p->normal_prio)) {
+                /*
+                 * Special case in which we have a !SCHED_DEADLINE task
+                 * that is going to be deboosted, but exceedes its
+                 * runtime while doing so. No point in replenishing
+                 * it, as it's going to return back to its original
+                 * scheduling class after this.
+                 */
+                BUG_ON(!p->dl.dl_boosted || flags != ENQUEUE_REPLENISH);
+                return;
+        }
 
         /*
          * If p is throttled, we do nothing. In fact, if it exhausted
@@ -1607,8 +1626,12 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
                         /* Only reschedule if pushing failed */
                         check_resched = 0;
 #endif /* CONFIG_SMP */
-                if (check_resched && task_has_dl_policy(rq->curr))
-                        check_preempt_curr_dl(rq, p, 0);
+                if (check_resched) {
+                        if (dl_task(rq->curr))
+                                check_preempt_curr_dl(rq, p, 0);
+                        else
+                                resched_curr(rq);
+                }
         }
 }
 
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 0b069bf3e708..34baa60f8a7b 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -828,11 +828,12 @@ static unsigned int task_nr_scan_windows(struct task_struct *p)
 
 static unsigned int task_scan_min(struct task_struct *p)
 {
+        unsigned int scan_size = ACCESS_ONCE(sysctl_numa_balancing_scan_size);
         unsigned int scan, floor;
         unsigned int windows = 1;
 
-        if (sysctl_numa_balancing_scan_size < MAX_SCAN_WINDOW)
-                windows = MAX_SCAN_WINDOW / sysctl_numa_balancing_scan_size;
+        if (scan_size < MAX_SCAN_WINDOW)
+                windows = MAX_SCAN_WINDOW / scan_size;
         floor = 1000 / windows;
 
         scan = sysctl_numa_balancing_scan_period_min / task_nr_scan_windows(p);
@@ -1164,9 +1165,19 @@ static void task_numa_compare(struct task_numa_env *env,
         long moveimp = imp;
 
         rcu_read_lock();
-        cur = ACCESS_ONCE(dst_rq->curr);
-        if (cur->pid == 0) /* idle */
+
+        raw_spin_lock_irq(&dst_rq->lock);
+        cur = dst_rq->curr;
+        /*
+         * No need to move the exiting task, and this ensures that ->curr
+         * wasn't reaped and thus get_task_struct() in task_numa_assign()
+         * is safe under RCU read lock.
+         * Note that rcu_read_lock() itself can't protect from the final
+         * put_task_struct() after the last schedule().
+         */
+        if ((cur->flags & PF_EXITING) || is_idle_task(cur))
                 cur = NULL;
+        raw_spin_unlock_irq(&dst_rq->lock);
 
         /*
          * "imp" is the fault differential for the source task between the
@@ -1520,7 +1531,7 @@ static void update_task_scan_period(struct task_struct *p,
                  * scanning faster if shared accesses dominate as it may
                  * simply bounce migrations uselessly
                  */
-                ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared));
+                ratio = DIV_ROUND_UP(private * NUMA_PERIOD_SLOTS, (private + shared + 1));
                 diff = (diff * ratio) / NUMA_PERIOD_SLOTS;
         }
 
diff --git a/kernel/sysctl.c b/kernel/sysctl.c
index 4aada6d9fe74..15f2511a1b7c 100644
--- a/kernel/sysctl.c
+++ b/kernel/sysctl.c
@@ -387,7 +387,8 @@ static struct ctl_table kern_table[] = {
                 .data           = &sysctl_numa_balancing_scan_size,
                 .maxlen         = sizeof(unsigned int),
                 .mode           = 0644,
-                .proc_handler   = proc_dointvec,
+                .proc_handler   = proc_dointvec_minmax,
+                .extra1         = &one,
         },
         {
                 .procname       = "numa_balancing",