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

From: Paul Menage
Date: Mon Jan 24 2011 - 03:38:41 EST

Hi Ben,

Finally finding a moment to actually look at these patches. Sorry it's
been a while. Can you send the patches inline rather than as
attachments in future?

Reviewed-by: Paul Menage <menage@xxxxxxxxxx>

This patch looks fine, although I think that freezer_can_attach_task()
could be simplified to:

static int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
{
if (__cgroup_freezing_or_frozen(tsk))
return -EBUSY;
return 0;
}

since we guarantee that rcu_read_lock() is held across this call.

There appears to be a tiny bit of rot in kernel/cpu.c (due to the
addition of the exit() callback) and memcontrol.c (due to some changes
at the start of mem_cgroup_move_task()) but neither impact actual
code.

I think that before actually pushing to mainline, we'll need to sort
out the cpuset mempolicy yielding issue, since that could be a
user-visible API change.


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

From: Ben Blum <bblum@xxxxxxxxxxxxxx>

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@xxxxxxxxxxxxxx>
---
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;