1 files changed, 108 insertions, 37 deletions

diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index d10946748ec2..02b9611eadde 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -946,16 +946,62 @@ static void cpuset_migrate_mm(struct mm_struct *mm, const nodemask_t *from,
  * In order to avoid seeing no nodes if the old and new nodes are disjoint,
  * we structure updates as setting all new allowed nodes, then clearing newly
  * disallowed ones.
- *
- * Called with task's alloc_lock held
  */
 static void cpuset_change_task_nodemask(struct task_struct *tsk,
                                         nodemask_t *newmems)
 {
+repeat:
+        /*
+         * Allow tasks that have access to memory reserves because they have
+         * been OOM killed to get memory anywhere.
+         */
+        if (unlikely(test_thread_flag(TIF_MEMDIE)))
+                return;
+        if (current->flags & PF_EXITING) /* Let dying task have memory */
+                return;
+
+        task_lock(tsk);
         nodes_or(tsk->mems_allowed, tsk->mems_allowed, *newmems);
-        mpol_rebind_task(tsk, &tsk->mems_allowed);
-        mpol_rebind_task(tsk, newmems);
+        mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP1);
+
+
+        /*
+         * ensure checking ->mems_allowed_change_disable after setting all new
+         * allowed nodes.
+         *
+         * the read-side task can see an nodemask with new allowed nodes and
+         * old allowed nodes. and if it allocates page when cpuset clears newly
+         * disallowed ones continuous, it can see the new allowed bits.
+         *
+         * And if setting all new allowed nodes is after the checking, setting
+         * all new allowed nodes and clearing newly disallowed ones will be done
+         * continuous, and the read-side task may find no node to alloc page.
+         */
+        smp_mb();
+
+        /*
+         * Allocation of memory is very fast, we needn't sleep when waiting
+         * for the read-side.
+         */
+        while (ACCESS_ONCE(tsk->mems_allowed_change_disable)) {
+                task_unlock(tsk);
+                if (!task_curr(tsk))
+                        yield();
+                goto repeat;
+        }
+
+        /*
+         * ensure checking ->mems_allowed_change_disable before clearing all new
+         * disallowed nodes.
+         *
+         * if clearing newly disallowed bits before the checking, the read-side
+         * task may find no node to alloc page.
+         */
+        smp_mb();
+
+        mpol_rebind_task(tsk, newmems, MPOL_REBIND_STEP2);
         tsk->mems_allowed = *newmems;
+        task_unlock(tsk);
 }
 
 /*
@@ -978,9 +1024,7 @@ static void cpuset_change_nodemask(struct task_struct *p,
         cs = cgroup_cs(scan->cg);
         guarantee_online_mems(cs, newmems);
 
-        task_lock(p);
         cpuset_change_task_nodemask(p, newmems);
-        task_unlock(p);
 
         NODEMASK_FREE(newmems);
 
@@ -1383,9 +1427,7 @@ static void cpuset_attach_task(struct task_struct *tsk, nodemask_t *to,
         err = set_cpus_allowed_ptr(tsk, cpus_attach);
         WARN_ON_ONCE(err);
 
-        task_lock(tsk);
         cpuset_change_task_nodemask(tsk, to);
-        task_unlock(tsk);
         cpuset_update_task_spread_flag(cs, tsk);
 
 }
@@ -2182,19 +2224,52 @@ void __init cpuset_init_smp(void)
 void cpuset_cpus_allowed(struct task_struct *tsk, struct cpumask *pmask)
 {
         mutex_lock(&callback_mutex);
-        cpuset_cpus_allowed_locked(tsk, pmask);
+        task_lock(tsk);
+        guarantee_online_cpus(task_cs(tsk), pmask);
+        task_unlock(tsk);
         mutex_unlock(&callback_mutex);
 }
 
-/**
- * cpuset_cpus_allowed_locked - return cpus_allowed mask from a tasks cpuset.
- * Must be called with callback_mutex held.
- **/
-void cpuset_cpus_allowed_locked(struct task_struct *tsk, struct cpumask *pmask)
+int cpuset_cpus_allowed_fallback(struct task_struct *tsk)
 {
-        task_lock(tsk);
-        guarantee_online_cpus(task_cs(tsk), pmask);
-        task_unlock(tsk);
+        const struct cpuset *cs;
+        int cpu;
+
+        rcu_read_lock();
+        cs = task_cs(tsk);
+        if (cs)
+                cpumask_copy(&tsk->cpus_allowed, cs->cpus_allowed);
+        rcu_read_unlock();
+
+        /*
+         * We own tsk->cpus_allowed, nobody can change it under us.
+         *
+         * But we used cs && cs->cpus_allowed lockless and thus can
+         * race with cgroup_attach_task() or update_cpumask() and get
+         * the wrong tsk->cpus_allowed. However, both cases imply the
+         * subsequent cpuset_change_cpumask()->set_cpus_allowed_ptr()
+         * which takes task_rq_lock().
+         *
+         * If we are called after it dropped the lock we must see all
+         * changes in tsk_cs()->cpus_allowed. Otherwise we can temporary
+         * set any mask even if it is not right from task_cs() pov,
+         * the pending set_cpus_allowed_ptr() will fix things.
+         */
+
+        cpu = cpumask_any_and(&tsk->cpus_allowed, cpu_active_mask);
+        if (cpu >= nr_cpu_ids) {
+                /*
+                 * Either tsk->cpus_allowed is wrong (see above) or it
+                 * is actually empty. The latter case is only possible
+                 * if we are racing with remove_tasks_in_empty_cpuset().
+                 * Like above we can temporary set any mask and rely on
+                 * set_cpus_allowed_ptr() as synchronization point.
+                 */
+                cpumask_copy(&tsk->cpus_allowed, cpu_possible_mask);
+                cpu = cpumask_any(cpu_active_mask);
+        }
+
+        return cpu;
 }
 
 void cpuset_init_current_mems_allowed(void)
@@ -2383,22 +2458,6 @@ int __cpuset_node_allowed_hardwall(int node, gfp_t gfp_mask)
 }
 
 /**
- * cpuset_lock - lock out any changes to cpuset structures
- *
- * The out of memory (oom) code needs to mutex_lock cpusets
- * from being changed while it scans the tasklist looking for a
- * task in an overlapping cpuset.  Expose callback_mutex via this
- * cpuset_lock() routine, so the oom code can lock it, before
- * locking the task list.  The tasklist_lock is a spinlock, so
- * must be taken inside callback_mutex.
- */
-
-void cpuset_lock(void)
-{
-        mutex_lock(&callback_mutex);
-}
-
-/**
  * cpuset_unlock - release lock on cpuset changes
  *
  * Undo the lock taken in a previous cpuset_lock() call.
@@ -2410,7 +2469,8 @@ void cpuset_unlock(void)
 }
 
 /**
- * cpuset_mem_spread_node() - On which node to begin search for a page
+ * cpuset_mem_spread_node() - On which node to begin search for a file page
+ * cpuset_slab_spread_node() - On which node to begin search for a slab page
  *
  * If a task is marked PF_SPREAD_PAGE or PF_SPREAD_SLAB (as for
  * tasks in a cpuset with is_spread_page or is_spread_slab set),
@@ -2435,16 +2495,27 @@ void cpuset_unlock(void)
  * See kmem_cache_alloc_node().
  */
 
-int cpuset_mem_spread_node(void)
+static int cpuset_spread_node(int *rotor)
 {
         int node;
 
-        node = next_node(current->cpuset_mem_spread_rotor, current->mems_allowed);
+        node = next_node(*rotor, current->mems_allowed);
         if (node == MAX_NUMNODES)
                 node = first_node(current->mems_allowed);
-        current->cpuset_mem_spread_rotor = node;
+        *rotor = node;
         return node;
 }
+
+int cpuset_mem_spread_node(void)
+{
+        return cpuset_spread_node(&current->cpuset_mem_spread_rotor);
+}
+
+int cpuset_slab_spread_node(void)
+{
+        return cpuset_spread_node(&current->cpuset_slab_spread_rotor);
+}
+
 EXPORT_SYMBOL_GPL(cpuset_mem_spread_node);
 
 /**