diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index aedf1bd..b3bd3bd 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -575,7 +575,7 @@
 called multiple times against a cgroup.
 
 int can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
-	       struct task_struct *task, bool threadgroup)
+	       struct task_struct *task)
 (cgroup_mutex held by caller)
 
 Called prior to moving a task into a cgroup; if the subsystem
@@ -584,9 +584,14 @@
 unspecified task can be moved into the cgroup. Note that this isn't
 called on a fork. If this method returns 0 (success) then this should
 remain valid while the caller holds cgroup_mutex and it is ensured that either
-attach() or cancel_attach() will be called in future. If threadgroup is
-true, then a successful result indicates that all threads in the given
-thread's threadgroup can be moved together.
+attach() or cancel_attach() will be called in future.
+
+int can_attach_task(struct cgroup *cgrp, struct task_struct *tsk);
+(cgroup_mutex held by caller)
+
+As can_attach, but for operations that must be run once per task to be
+attached (possibly many when using cgroup_attach_proc). Called after
+can_attach.
 
 void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
 	       struct task_struct *task, bool threadgroup)
@@ -598,15 +603,24 @@
 This will be called only about subsystems whose can_attach() operation have
 succeeded.
 
+void pre_attach(struct cgroup *cgrp);
+(cgroup_mutex held by caller)
+
+For any non-per-thread attachment work that needs to happen before
+attach_task. Needed by cpuset.
+
 void attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
-	    struct cgroup *old_cgrp, struct task_struct *task,
-	    bool threadgroup)
+	    struct cgroup *old_cgrp, struct task_struct *task)
 (cgroup_mutex held by caller)
 
 Called after the task has been attached to the cgroup, to allow any
 post-attachment activity that requires memory allocations or blocking.
-If threadgroup is true, the subsystem should take care of all threads
-in the specified thread's threadgroup. Currently does not support any
+
+void attach_task(struct cgroup *cgrp, struct task_struct *tsk);
+(cgroup_mutex held by caller)
+
+As attach, but for operations that must be run once per task to be attached,
+like can_attach_task. Called before attach. Currently does not support any
 subsystem that might need the old_cgrp for every thread in the group.
 
 void fork(struct cgroup_subsy *ss, struct task_struct *task)
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index 07371cf..bcaf16e 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -30,10 +30,8 @@
 
 static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
 						  struct cgroup *);
-static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
-			      struct task_struct *, bool);
-static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
-			   struct cgroup *, struct task_struct *, bool);
+static int blkiocg_can_attach_task(struct cgroup *, struct task_struct *);
+static void blkiocg_attach_task(struct cgroup *, struct task_struct *);
 static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
 static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 
@@ -46,8 +44,8 @@
 struct cgroup_subsys blkio_subsys = {
 	.name = "blkio",
 	.create = blkiocg_create,
-	.can_attach = blkiocg_can_attach,
-	.attach = blkiocg_attach,
+	.can_attach_task = blkiocg_can_attach_task,
+	.attach_task = blkiocg_attach_task,
 	.destroy = blkiocg_destroy,
 	.populate = blkiocg_populate,
 #ifdef CONFIG_BLK_CGROUP
@@ -1616,9 +1614,7 @@
  * of the main cic data structures.  For now we allow a task to change
  * its cgroup only if it's the only owner of its ioc.
  */
-static int blkiocg_can_attach(struct cgroup_subsys *subsys,
-				struct cgroup *cgroup, struct task_struct *tsk,
-				bool threadgroup)
+static int blkiocg_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 {
 	struct io_context *ioc;
 	int ret = 0;
@@ -1633,9 +1629,7 @@
 	return ret;
 }
 
-static void blkiocg_attach(struct cgroup_subsys *subsys, struct cgroup *cgroup,
-				struct cgroup *prev, struct task_struct *tsk,
-				bool threadgroup)
+static void blkiocg_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 {
 	struct io_context *ioc;
 
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 5ac7ebc..1e6cde2 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -467,12 +467,14 @@
 	int (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 	void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);
 	int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
-			  struct task_struct *tsk, bool threadgroup);
+			  struct task_struct *tsk);
+	int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
 	void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
-			  struct task_struct *tsk, bool threadgroup);
+			      struct task_struct *tsk);
+	void (*pre_attach)(struct cgroup *cgrp);
+	void (*attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
 	void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
-			struct cgroup *old_cgrp, struct task_struct *tsk,
-			bool threadgroup);
+		       struct cgroup *old_cgrp, struct task_struct *tsk);
 	void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
 	void (*exit)(struct cgroup_subsys *ss, struct cgroup *cgrp,
 			struct cgroup *old_cgrp, struct task_struct *task);
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 909a355..38fb0ad 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1759,7 +1759,7 @@
 
 	for_each_subsys(root, ss) {
 		if (ss->can_attach) {
-			retval = ss->can_attach(ss, cgrp, tsk, false);
+			retval = ss->can_attach(ss, cgrp, tsk);
 			if (retval) {
 				/*
 				 * Remember on which subsystem the can_attach()
@@ -1771,6 +1771,13 @@
 				goto out;
 			}
 		}
+		if (ss->can_attach_task) {
+			retval = ss->can_attach_task(cgrp, tsk);
+			if (retval) {
+				failed_ss = ss;
+				goto out;
+			}
+		}
 	}
 
 	task_lock(tsk);
@@ -1805,8 +1812,12 @@
 	write_unlock(&css_set_lock);
 
 	for_each_subsys(root, ss) {
+		if (ss->pre_attach)
+			ss->pre_attach(cgrp);
+		if (ss->attach_task)
+			ss->attach_task(cgrp, tsk);
 		if (ss->attach)
-			ss->attach(ss, cgrp, oldcgrp, tsk, false);
+			ss->attach(ss, cgrp, oldcgrp, tsk);
 	}
 	set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
 	synchronize_rcu();
@@ -1829,7 +1840,7 @@
 				 */
 				break;
 			if (ss->cancel_attach)
-				ss->cancel_attach(ss, cgrp, tsk, false);
+				ss->cancel_attach(ss, cgrp, tsk);
 		}
 	}
 	return retval;
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index e7bebb7..e691818 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -160,7 +160,7 @@
  */
 static int freezer_can_attach(struct cgroup_subsys *ss,
 			      struct cgroup *new_cgroup,
-			      struct task_struct *task, bool threadgroup)
+			      struct task_struct *task)
 {
 	struct freezer *freezer;
 
@@ -172,26 +172,17 @@
 	if (freezer->state != CGROUP_THAWED)
 		return -EBUSY;
 
+	return 0;
+}
+
+static int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+{
 	rcu_read_lock();
-	if (__cgroup_freezing_or_frozen(task)) {
+	if (__cgroup_freezing_or_frozen(tsk)) {
 		rcu_read_unlock();
 		return -EBUSY;
 	}
 	rcu_read_unlock();
-
-	if (threadgroup) {
-		struct task_struct *c;
-
-		rcu_read_lock();
-		list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
-			if (__cgroup_freezing_or_frozen(c)) {
-				rcu_read_unlock();
-				return -EBUSY;
-			}
-		}
-		rcu_read_unlock();
-	}
-
 	return 0;
 }
 
@@ -390,6 +381,9 @@
 	.populate	= freezer_populate,
 	.subsys_id	= freezer_subsys_id,
 	.can_attach	= freezer_can_attach,
+	.can_attach_task = freezer_can_attach_task,
+	.pre_attach	= NULL,
+	.attach_task	= NULL,
 	.attach		= NULL,
 	.fork		= freezer_fork,
 	.exit		= NULL,
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 2bb8c2e..55b297d 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1367,14 +1367,10 @@
 	return val;
 }
 
-/* Protected by cgroup_lock */
-static cpumask_var_t cpus_attach;
-
 /* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
 static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
-			     struct task_struct *tsk, bool threadgroup)
+			     struct task_struct *tsk)
 {
-	int ret;
 	struct cpuset *cs = cgroup_cs(cont);
 
 	if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
@@ -1391,29 +1387,42 @@
 	if (tsk->flags & PF_THREAD_BOUND)
 		return -EINVAL;
 
-	ret = security_task_setscheduler(tsk);
-	if (ret)
-		return ret;
-	if (threadgroup) {
-		struct task_struct *c;
-
-		rcu_read_lock();
-		list_for_each_entry_rcu(c, &tsk->thread_group, thread_group) {
-			ret = security_task_setscheduler(c);
-			if (ret) {
-				rcu_read_unlock();
-				return ret;
-			}
-		}
-		rcu_read_unlock();
-	}
 	return 0;
 }
 
-static void cpuset_attach_task(struct task_struct *tsk, nodemask_t *to,
-			       struct cpuset *cs)
+static int cpuset_can_attach_task(struct cgroup *cgrp, struct task_struct *task)
+{
+	return security_task_setscheduler(task);
+}
+
+/*
+ * Protected by cgroup_lock. The nodemasks must be stored globally because
+ * dynamically allocating them is not allowed in pre_attach, and they must
+ * persist among pre_attach, attach_task, and attach.
+ */
+static cpumask_var_t cpus_attach;
+static nodemask_t cpuset_attach_nodemask_from;
+static nodemask_t cpuset_attach_nodemask_to;
+
+/* Set-up work for before attaching each task. */
+static void cpuset_pre_attach(struct cgroup *cont)
+{
+	struct cpuset *cs = cgroup_cs(cont);
+
+	if (cs == &top_cpuset)
+		cpumask_copy(cpus_attach, cpu_possible_mask);
+	else
+		guarantee_online_cpus(cs, cpus_attach);
+
+	guarantee_online_mems(cs, &cpuset_attach_nodemask_to);
+}
+
+/* Per-thread attachment work. */
+static void cpuset_attach_task(struct cgroup *cont, struct task_struct *tsk)
 {
 	int err;
+	struct cpuset *cs = cgroup_cs(cont);
+
 	/*
 	 * can_attach beforehand should guarantee that this doesn't fail.
 	 * TODO: have a better way to handle failure here
@@ -1421,45 +1430,29 @@
 	err = set_cpus_allowed_ptr(tsk, cpus_attach);
 	WARN_ON_ONCE(err);
 
-	cpuset_change_task_nodemask(tsk, to);
+	cpuset_change_task_nodemask(tsk, &cpuset_attach_nodemask_to);
 	cpuset_update_task_spread_flag(cs, tsk);
-
 }
 
 static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
-			  struct cgroup *oldcont, struct task_struct *tsk,
-			  bool threadgroup)
+			  struct cgroup *oldcont, struct task_struct *tsk)
 {
 	struct mm_struct *mm;
 	struct cpuset *cs = cgroup_cs(cont);
 	struct cpuset *oldcs = cgroup_cs(oldcont);
-	static nodemask_t to;		/* protected by cgroup_mutex */
 
-	if (cs == &top_cpuset) {
-		cpumask_copy(cpus_attach, cpu_possible_mask);
-	} else {
-		guarantee_online_cpus(cs, cpus_attach);
-	}
-	guarantee_online_mems(cs, &to);
-
-	/* do per-task migration stuff possibly for each in the threadgroup */
-	cpuset_attach_task(tsk, &to, cs);
-	if (threadgroup) {
-		struct task_struct *c;
-		rcu_read_lock();
-		list_for_each_entry_rcu(c, &tsk->thread_group, thread_group) {
-			cpuset_attach_task(c, &to, cs);
-		}
-		rcu_read_unlock();
-	}
-
-	/* change mm; only needs to be done once even if threadgroup */
-	to = cs->mems_allowed;
+	/*
+	 * Change mm, possibly for multiple threads in a threadgroup. This is
+	 * expensive and may sleep.
+	 */
+	cpuset_attach_nodemask_from = oldcs->mems_allowed;
+	cpuset_attach_nodemask_to = cs->mems_allowed;
 	mm = get_task_mm(tsk);
 	if (mm) {
-		mpol_rebind_mm(mm, &to);
+		mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
 		if (is_memory_migrate(cs))
-			cpuset_migrate_mm(mm, &oldcs->mems_allowed, &to);
+			cpuset_migrate_mm(mm, &cpuset_attach_nodemask_from,
+					  &cpuset_attach_nodemask_to);
 		mmput(mm);
 	}
 }
@@ -1911,6 +1904,9 @@
 	.create = cpuset_create,
 	.destroy = cpuset_destroy,
 	.can_attach = cpuset_can_attach,
+	.can_attach_task = cpuset_can_attach_task,
+	.pre_attach = cpuset_pre_attach,
+	.attach_task = cpuset_attach_task,
 	.attach = cpuset_attach,
 	.populate = cpuset_populate,
 	.post_clone = cpuset_post_clone,
diff --git a/kernel/sched.c b/kernel/sched.c
index 2d12893..5e43e9d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8764,42 +8764,10 @@
 	return 0;
 }
 
-static int
-cpu_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
-		      struct task_struct *tsk, bool threadgroup)
-{
-	int retval = cpu_cgroup_can_attach_task(cgrp, tsk);
-	if (retval)
-		return retval;
-	if (threadgroup) {
-		struct task_struct *c;
-		rcu_read_lock();
-		list_for_each_entry_rcu(c, &tsk->thread_group, thread_group) {
-			retval = cpu_cgroup_can_attach_task(cgrp, c);
-			if (retval) {
-				rcu_read_unlock();
-				return retval;
-			}
-		}
-		rcu_read_unlock();
-	}
-	return 0;
-}
-
 static void
-cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
-		  struct cgroup *old_cont, struct task_struct *tsk,
-		  bool threadgroup)
+cpu_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 {
 	sched_move_task(tsk);
-	if (threadgroup) {
-		struct task_struct *c;
-		rcu_read_lock();
-		list_for_each_entry_rcu(c, &tsk->thread_group, thread_group) {
-			sched_move_task(c);
-		}
-		rcu_read_unlock();
-	}
 }
 
 static void
@@ -8887,8 +8855,8 @@
 	.name		= "cpu",
 	.create		= cpu_cgroup_create,
 	.destroy	= cpu_cgroup_destroy,
-	.can_attach	= cpu_cgroup_can_attach,
-	.attach		= cpu_cgroup_attach,
+	.can_attach_task = cpu_cgroup_can_attach_task,
+	.attach_task	= cpu_cgroup_attach_task,
 	.exit		= cpu_cgroup_exit,
 	.populate	= cpu_cgroup_populate,
 	.subsys_id	= cpu_cgroup_subsys_id,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d5fd3dc..fc25992 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4953,8 +4953,7 @@
 
 static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p,
-				bool threadgroup)
+				struct task_struct *p)
 {
 	int ret = 0;
 	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
@@ -4993,8 +4992,7 @@
 
 static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p,
-				bool threadgroup)
+				struct task_struct *p)
 {
 	mem_cgroup_clear_mc();
 }
@@ -5112,8 +5110,7 @@
 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
 				struct cgroup *cont,
 				struct cgroup *old_cont,
-				struct task_struct *p,
-				bool threadgroup)
+				struct task_struct *p)
 {
 	struct mm_struct *mm;
 
@@ -5131,22 +5128,19 @@
 #else	/* !CONFIG_MMU */
 static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p,
-				bool threadgroup)
+				struct task_struct *p)
 {
 	return 0;
 }
 static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p,
-				bool threadgroup)
+				struct task_struct *p)
 {
 }
 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
 				struct cgroup *cont,
 				struct cgroup *old_cont,
-				struct task_struct *p,
-				bool threadgroup)
+				struct task_struct *p)
 {
 }
 #endif
diff --git a/security/device_cgroup.c b/security/device_cgroup.c
index 8d9c48f..cd1f779 100644
--- a/security/device_cgroup.c
+++ b/security/device_cgroup.c
@@ -62,8 +62,7 @@
 struct cgroup_subsys devices_subsys;
 
 static int devcgroup_can_attach(struct cgroup_subsys *ss,
-		struct cgroup *new_cgroup, struct task_struct *task,
-		bool threadgroup)
+		struct cgroup *new_cgroup, struct task_struct *task)
 {
 	if (current != task && !capable(CAP_SYS_ADMIN))
 			return -EPERM;