[PATCH v7 2/3] cgroups: add atomic-context per-thread subsystem callbacks

[Ben Blum <bblum@andrew.cmu.edu>]

[-- Attachment #1: cgroup-subsys-task-callbacks.patch --]
[-- Type: text/plain, Size: 22352 bytes --]

Add cgroup subsystem callbacks for per-thread attachment in atomic contexts

From: Ben Blum <bblum@andrew.cmu.edu>

This patch adds can_attach_task, pre_attach, and attach_task as new callbacks
for cgroups's subsystem interface. Unlike can_attach and attach, these are for
per-thread operations, to be called potentially many times when attaching an
entire threadgroup, and may run under rcu_read/tasklist_lock, so are for quick
operations only.

Also, the old "bool threadgroup" interface is removed, as replaced by this.
All subsystems are modified for the new interface - of note is cpuset, which
requires from/to nodemasks for attach to be globally scoped (though per-cpuset
would work too) to persist from its pre_attach to attach_task and attach.

This is a pre-patch for cgroup-procs-writable.patch.

Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
---
 Documentation/cgroups/cgroups.txt |   35 ++++++++---
 Documentation/cgroups/cpusets.txt |    9 +++
 block/blk-cgroup.c                |   18 ++----
 include/linux/cgroup.h            |   10 ++-
 kernel/cgroup.c                   |   17 ++++-
 kernel/cgroup_freezer.c           |   27 ++++-----
 kernel/cpuset.c                   |  116 +++++++++++++++++++------------------
 kernel/ns_cgroup.c                |   23 +++----
 kernel/sched.c                    |   38 +-----------
 mm/memcontrol.c                   |   18 ++----
 security/device_cgroup.c          |    3 -
 11 files changed, 149 insertions(+), 165 deletions(-)

diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 190018b..341ed44 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -563,7 +563,7 @@ rmdir() will fail with it. From this behavior, pre_destroy() can be
 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
@@ -572,9 +572,15 @@ task is passed, then a successful result indicates that *any*
 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 and rcu_read_lock 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). This may run in
+rcu_read-side, so sleeping is not permitted. Expensive operations, such as
+dealing with the shared mm, should run in can_attach.
 
 void cancel_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
 	       struct task_struct *task, bool threadgroup)
@@ -587,15 +593,26 @@ This will be called only about subsystems whose can_attach() operation have
 succeeded.
 
 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
-subsystem that might need the old_cgrp for every thread in the group.
+
+void pre_attach(struct cgroup *cgrp);
+(cgroup_mutex and tasklist_lock held by caller)
+
+See description of attach_task.
+
+void attach_task(struct cgroup *cgrp, struct task_struct *tsk);
+(cgroup_mutex and possibly tasklist_lock held by caller)
+
+As attach, but for operations that must be run once per task to be attached,
+like can_attach_task. Sometimes called with tasklist_lock taken for reading,
+so may not sleep. Currently does not support any subsystem that might need the
+old_cgrp for every thread in the group. Note: unlike can_attach_task, this
+runs before attach, so use pre_attach for non-per-thread operations that must
+happen before attach_task.
 
 void fork(struct cgroup_subsy *ss, struct task_struct *task)
 
diff --git a/Documentation/cgroups/cpusets.txt b/Documentation/cgroups/cpusets.txt
index 5d0d569..1f0868d 100644
--- a/Documentation/cgroups/cpusets.txt
+++ b/Documentation/cgroups/cpusets.txt
@@ -659,6 +659,15 @@ the current task's cpuset, then we relax the cpuset, and look for
 memory anywhere we can find it.  It's better to violate the cpuset
 than stress the kernel.
 
+There is a third exception to the above.  When using the cgroup.procs file
+to move all tasks in a threadgroup at once, the per-task attachment code
+must run in an atomic context, but as currently implemented, changing the
+nodemasks for a task's memory policy may need to deschedule.  So, in this
+case, the best cpusets can do is change the nodemask for the threadgroup
+leader when attaching.  Thus, a multithreaded mempolicy user should first
+use cgroup.procs (for correctness), but also next use the tasks file for
+each thread in the group to ensure updating the nodemasks for all of them.
+
 To start a new job that is to be contained within a cpuset, the steps are:
 
  1) mkdir /dev/cpuset
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b1febd0..45b3809 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -30,10 +30,8 @@ EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
 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 @@ static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 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
@@ -1475,9 +1473,7 @@ done:
  * 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;
@@ -1492,9 +1488,7 @@ static int blkiocg_can_attach(struct cgroup_subsys *subsys,
 	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 ce104e3..35b69b4 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -467,12 +467,14 @@ struct cgroup_subsys {
 	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 task_struct *task);
 	int (*populate)(struct cgroup_subsys *ss,
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 66a416b..616f27a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1750,7 +1750,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 
 	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()
@@ -1762,6 +1762,13 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 				goto out;
 			}
 		}
+		if (ss->can_attach_task) {
+			retval = ss->can_attach_task(cgrp, tsk);
+			if (retval) {
+				failed_ss = ss;
+				goto out;
+			}
+		}
 	}
 
 	task_lock(tsk);
@@ -1798,8 +1805,12 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 	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();
@@ -1822,7 +1833,7 @@ out:
 				 */
 				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..e6ee70c 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -160,7 +160,7 @@ static void freezer_destroy(struct cgroup_subsys *ss,
  */
 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 +172,18 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
 	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 allows recursive locking */
 	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 +382,9 @@ struct cgroup_subsys freezer_subsys = {
 	.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 4349935..b9fce80 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -1372,14 +1372,10 @@ static int fmeter_getrate(struct fmeter *fmp)
 	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))
@@ -1396,29 +1392,42 @@ static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cont,
 	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;
+
+/* Do quick 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
@@ -1426,56 +1435,46 @@ static void cpuset_attach_task(struct task_struct *tsk, nodemask_t *to,
 	err = set_cpus_allowed_ptr(tsk, cpus_attach);
 	WARN_ON_ONCE(err);
 
-	cpuset_change_task_nodemask(tsk, 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);
-	NODEMASK_ALLOC(nodemask_t, from, GFP_KERNEL);
-	NODEMASK_ALLOC(nodemask_t, to, GFP_KERNEL);
 
-	if (from == NULL || to == NULL)
-		goto alloc_fail;
-
-	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();
-	}
+	/*
+	 * TODO: As implemented, change_task_nodemask uses yield() to
+	 * synchronize with other users of the mems_allowed, which is not
+	 * allowed in the atomic attach_task callback, so we can't do this for
+	 * each thread in the multithreaded case. This is a performance issue,
+	 * but not a correctness one.
+	 *
+	 * As long as change_task_nodemask can yield, a multithreaded mempolicy
+	 * user should attach to a cgroup by threadgroup first (for
+	 * correctness) then poke each task to get its mempolicy right.
+	 *
+	 * This is the "third exception" in Documentation/cgroups/cpusets.txt.
+	 */
+	cpuset_change_task_nodemask(tsk, &cpuset_attach_nodemask_to);
 
-	/* change mm; only needs to be done once even if threadgroup */
-	*from = oldcs->mems_allowed;
-	*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, from, to);
+			cpuset_migrate_mm(mm, &cpuset_attach_nodemask_from,
+					  &cpuset_attach_nodemask_to);
 		mmput(mm);
 	}
-
-alloc_fail:
-	NODEMASK_FREE(from);
-	NODEMASK_FREE(to);
 }
 
 /* The various types of files and directories in a cpuset file system */
@@ -1928,6 +1927,9 @@ struct cgroup_subsys cpuset_subsys = {
 	.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/ns_cgroup.c b/kernel/ns_cgroup.c
index 2c98ad9..1fc2b1b 100644
--- a/kernel/ns_cgroup.c
+++ b/kernel/ns_cgroup.c
@@ -43,7 +43,7 @@ int ns_cgroup_clone(struct task_struct *task, struct pid *pid)
  *        ancestor cgroup thereof)
  */
 static int ns_can_attach(struct cgroup_subsys *ss, struct cgroup *new_cgroup,
-			 struct task_struct *task, bool threadgroup)
+			 struct task_struct *task)
 {
 	if (current != task) {
 		if (!capable(CAP_SYS_ADMIN))
@@ -53,21 +53,13 @@ static int ns_can_attach(struct cgroup_subsys *ss, struct cgroup *new_cgroup,
 			return -EPERM;
 	}
 
-	if (!cgroup_is_descendant(new_cgroup, task))
-		return -EPERM;
-
-	if (threadgroup) {
-		struct task_struct *c;
-		rcu_read_lock();
-		list_for_each_entry_rcu(c, &task->thread_group, thread_group) {
-			if (!cgroup_is_descendant(new_cgroup, c)) {
-				rcu_read_unlock();
-				return -EPERM;
-			}
-		}
-		rcu_read_unlock();
-	}
+	return 0;
+}
 
+static int ns_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+{
+	if (!cgroup_is_descendant(cgrp, tsk))
+		return -EPERM;
 	return 0;
 }
 
@@ -112,6 +104,7 @@ static void ns_destroy(struct cgroup_subsys *ss,
 struct cgroup_subsys ns_subsys = {
 	.name = "ns",
 	.can_attach = ns_can_attach,
+	.can_attach_task = ns_can_attach_task,
 	.create = ns_create,
 	.destroy  = ns_destroy,
 	.subsys_id = ns_subsys_id,
diff --git a/kernel/sched.c b/kernel/sched.c
index 218ef20..d619f1d 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -8655,42 +8655,10 @@ cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 	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();
-	}
 }
 
 #ifdef CONFIG_FAIR_GROUP_SCHED
@@ -8763,8 +8731,8 @@ struct cgroup_subsys cpu_cgroup_subsys = {
 	.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,
 	.populate	= cpu_cgroup_populate,
 	.subsys_id	= cpu_cgroup_subsys_id,
 	.early_init	= 1,
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 729beb7..995f0b9 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -4720,8 +4720,7 @@ static void mem_cgroup_clear_mc(void)
 
 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);
@@ -4775,8 +4774,7 @@ static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 
 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();
 }
@@ -4880,8 +4878,7 @@ static void mem_cgroup_move_charge(struct mm_struct *mm)
 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)
 {
 	if (!mc.mm)
 		/* no need to move charge */
@@ -4893,22 +4890,19 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss,
 #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 @@ static inline struct dev_cgroup *task_devcgroup(struct task_struct *task)
 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;