Merge branch 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup

* 'for-3.3' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (21 commits)
  cgroup: fix to allow mounting a hierarchy by name
  cgroup: move assignement out of condition in cgroup_attach_proc()
  cgroup: Remove task_lock() from cgroup_post_fork()
  cgroup: add sparse annotation to cgroup_iter_start() and cgroup_iter_end()
  cgroup: mark cgroup_rmdir_waitq and cgroup_attach_proc() as static
  cgroup: only need to check oldcgrp==newgrp once
  cgroup: remove redundant get/put of task struct
  cgroup: remove redundant get/put of old css_set from migrate
  cgroup: Remove unnecessary task_lock before fetching css_set on migration
  cgroup: Drop task_lock(parent) on cgroup_fork()
  cgroups: remove redundant get/put of css_set from css_set_check_fetched()
  resource cgroups: remove bogus cast
  cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task()
  cgroup, cpuset: don't use ss->pre_attach()
  cgroup: don't use subsys->can_attach_task() or ->attach_task()
  cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach()
  cgroup: improve old cgroup handling in cgroup_attach_proc()
  cgroup: always lock threadgroup during migration
  threadgroup: extend threadgroup_lock() to cover exit and exec
  threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem
  ...

Fix up conflict in kernel/cgroup.c due to commit e0197aae: "cgroups:
fix a css_set not found bug in cgroup_attach_proc" that already
mentioned that the bug is fixed (differently) in Tejun's cgroup
patchset. This one, in other words.

Documentation/cgroups/cgroups.txt

@@ -594,53 +594,44 @@ 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)
+	       struct cgroup_taskset *tset)
 (cgroup_mutex held by caller)
 
-Called prior to moving a task into a cgroup; if the subsystem
-returns an error, this will abort the attach operation.  If a NULL
-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
+Called prior to moving one or more tasks into a cgroup; if the
+subsystem returns an error, this will abort the attach operation.
+@tset contains the tasks to be attached and is guaranteed to have at
+least one task in it.
+
+If there are multiple tasks in the taskset, then:
+  - it's guaranteed that all are from the same thread group
+  - @tset contains all tasks from the thread group whether or not
+    they're switching cgroups
+  - the first task is the leader
+
+Each @tset entry also contains the task's old cgroup and tasks which
+aren't switching cgroup can be skipped easily using the
+cgroup_taskset_for_each() iterator. 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.
 
-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)
+		   struct cgroup_taskset *tset)
 (cgroup_mutex held by caller)
 
 Called when a task attach operation has failed after can_attach() has succeeded.
 A subsystem whose can_attach() has some side-effects should provide this
 function, so that the subsystem can implement a rollback. If not, not necessary.
 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.
+succeeded. The parameters are identical to can_attach().
 
 void attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
-	    struct cgroup *old_cgrp, struct task_struct *task)
+	    struct cgroup_taskset *tset)
 (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.
-
-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.
+The parameters are identical to can_attach().
 
 void fork(struct cgroup_subsy *ss, struct task_struct *task)
 

block/blk-cgroup.c

@@ -30,8 +30,10 @@ EXPORT_SYMBOL_GPL(blkio_root_cgroup);
 
 static struct cgroup_subsys_state *blkiocg_create(struct cgroup_subsys *,
 						  struct cgroup *);
-static int blkiocg_can_attach_task(struct cgroup *, struct task_struct *);
-static void blkiocg_attach_task(struct cgroup *, struct task_struct *);
+static int blkiocg_can_attach(struct cgroup_subsys *, struct cgroup *,
+			      struct cgroup_taskset *);
+static void blkiocg_attach(struct cgroup_subsys *, struct cgroup *,
+			   struct cgroup_taskset *);
 static void blkiocg_destroy(struct cgroup_subsys *, struct cgroup *);
 static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 
@@ -44,8 +46,8 @@ static int blkiocg_populate(struct cgroup_subsys *, struct cgroup *);
 struct cgroup_subsys blkio_subsys = {
 	.name = "blkio",
 	.create = blkiocg_create,
-	.can_attach_task = blkiocg_can_attach_task,
-	.attach_task = blkiocg_attach_task,
+	.can_attach = blkiocg_can_attach,
+	.attach = blkiocg_attach,
 	.destroy = blkiocg_destroy,
 	.populate = blkiocg_populate,
 #ifdef CONFIG_BLK_CGROUP
@@ -1626,30 +1628,39 @@ blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
  * 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_task(struct cgroup *cgrp, struct task_struct *tsk)
+static int blkiocg_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			      struct cgroup_taskset *tset)
 {
+	struct task_struct *task;
 	struct io_context *ioc;
 	int ret = 0;
 
 	/* task_lock() is needed to avoid races with exit_io_context() */
-	task_lock(tsk);
-	ioc = tsk->io_context;
+	cgroup_taskset_for_each(task, cgrp, tset) {
+		task_lock(task);
+		ioc = task->io_context;
 		if (ioc && atomic_read(&ioc->nr_tasks) > 1)
 			ret = -EINVAL;
-	task_unlock(tsk);
-
+		task_unlock(task);
+		if (ret)
+			break;
+	}
 	return ret;
 }
 
-static void blkiocg_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+static void blkiocg_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			   struct cgroup_taskset *tset)
 {
+	struct task_struct *task;
 	struct io_context *ioc;
 
-	task_lock(tsk);
-	ioc = tsk->io_context;
+	cgroup_taskset_for_each(task, cgrp, tset) {
+		task_lock(task);
+		ioc = task->io_context;
 		if (ioc)
 			ioc->cgroup_changed = 1;
-	task_unlock(tsk);
+		task_unlock(task);
+	}
 }
 
 void blkio_policy_register(struct blkio_policy_type *blkiop)

include/linux/cgroup.h

@@ -456,6 +456,28 @@ int cgroup_is_descendant(const struct cgroup *cgrp, struct task_struct *task);
 void cgroup_exclude_rmdir(struct cgroup_subsys_state *css);
 void cgroup_release_and_wakeup_rmdir(struct cgroup_subsys_state *css);
 
+/*
+ * Control Group taskset, used to pass around set of tasks to cgroup_subsys
+ * methods.
+ */
+struct cgroup_taskset;
+struct task_struct *cgroup_taskset_first(struct cgroup_taskset *tset);
+struct task_struct *cgroup_taskset_next(struct cgroup_taskset *tset);
+struct cgroup *cgroup_taskset_cur_cgroup(struct cgroup_taskset *tset);
+int cgroup_taskset_size(struct cgroup_taskset *tset);
+
+/**
+ * cgroup_taskset_for_each - iterate cgroup_taskset
+ * @task: the loop cursor
+ * @skip_cgrp: skip if task's cgroup matches this, %NULL to iterate through all
+ * @tset: taskset to iterate
+ */
+#define cgroup_taskset_for_each(task, skip_cgrp, tset)			\
+	for ((task) = cgroup_taskset_first((tset)); (task);		\
+	     (task) = cgroup_taskset_next((tset)))			\
+		if (!(skip_cgrp) ||					\
+		    cgroup_taskset_cur_cgroup((tset)) != (skip_cgrp))
+
 /*
  * Control Group subsystem type.
  * See Documentation/cgroups/cgroups.txt for details
@@ -467,14 +489,11 @@ 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);
-	int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
+			  struct cgroup_taskset *tset);
 	void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
-			      struct task_struct *tsk);
-	void (*pre_attach)(struct cgroup *cgrp);
-	void (*attach_task)(struct cgroup *cgrp, struct task_struct *tsk);
+			      struct cgroup_taskset *tset);
 	void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
-		       struct cgroup *old_cgrp, struct task_struct *tsk);
+		       struct cgroup_taskset *tset);
 	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);

include/linux/init_task.h

@@ -23,11 +23,10 @@ extern struct files_struct init_files;
 extern struct fs_struct init_fs;
 
 #ifdef CONFIG_CGROUPS
-#define INIT_THREADGROUP_FORK_LOCK(sig)					\
-	.threadgroup_fork_lock =					\
-		__RWSEM_INITIALIZER(sig.threadgroup_fork_lock),
+#define INIT_GROUP_RWSEM(sig)						\
+	.group_rwsem = __RWSEM_INITIALIZER(sig.group_rwsem),
 #else
-#define INIT_THREADGROUP_FORK_LOCK(sig)
+#define INIT_GROUP_RWSEM(sig)
 #endif
 
 #define INIT_SIGNALS(sig) {						\
@@ -46,7 +45,7 @@ extern struct fs_struct init_fs;
 	},								\
 	.cred_guard_mutex =						\
 		 __MUTEX_INITIALIZER(sig.cred_guard_mutex),		\
-	INIT_THREADGROUP_FORK_LOCK(sig)					\
+	INIT_GROUP_RWSEM(sig)						\
 }
 
 extern struct nsproxy init_nsproxy;

include/linux/sched.h

@@ -637,13 +637,15 @@ struct signal_struct {
 #endif
 #ifdef CONFIG_CGROUPS
 	/*
-	 * The threadgroup_fork_lock prevents threads from forking with
-	 * CLONE_THREAD while held for writing. Use this for fork-sensitive
-	 * threadgroup-wide operations. It's taken for reading in fork.c in
-	 * copy_process().
-	 * Currently only needed write-side by cgroups.
+	 * group_rwsem prevents new tasks from entering the threadgroup and
+	 * member tasks from exiting,a more specifically, setting of
+	 * PF_EXITING.  fork and exit paths are protected with this rwsem
+	 * using threadgroup_change_begin/end().  Users which require
+	 * threadgroup to remain stable should use threadgroup_[un]lock()
+	 * which also takes care of exec path.  Currently, cgroup is the
+	 * only user.
 	 */
-	struct rw_semaphore threadgroup_fork_lock;
+	struct rw_semaphore group_rwsem;
 #endif
 
 	int oom_adj;		/* OOM kill score adjustment (bit shift) */
@@ -2394,29 +2396,62 @@ static inline void unlock_task_sighand(struct task_struct *tsk,
 	spin_unlock_irqrestore(&tsk->sighand->siglock, *flags);
 }
 
-/* See the declaration of threadgroup_fork_lock in signal_struct. */
 #ifdef CONFIG_CGROUPS
-static inline void threadgroup_fork_read_lock(struct task_struct *tsk)
+static inline void threadgroup_change_begin(struct task_struct *tsk)
 {
-	down_read(&tsk->signal->threadgroup_fork_lock);
+	down_read(&tsk->signal->group_rwsem);
 }
-static inline void threadgroup_fork_read_unlock(struct task_struct *tsk)
+static inline void threadgroup_change_end(struct task_struct *tsk)
 {
-	up_read(&tsk->signal->threadgroup_fork_lock);
+	up_read(&tsk->signal->group_rwsem);
 }
-static inline void threadgroup_fork_write_lock(struct task_struct *tsk)
+
+/**
+ * threadgroup_lock - lock threadgroup
+ * @tsk: member task of the threadgroup to lock
+ *
+ * Lock the threadgroup @tsk belongs to.  No new task is allowed to enter
+ * and member tasks aren't allowed to exit (as indicated by PF_EXITING) or
+ * perform exec.  This is useful for cases where the threadgroup needs to
+ * stay stable across blockable operations.
+ *
+ * fork and exit paths explicitly call threadgroup_change_{begin|end}() for
+ * synchronization.  While held, no new task will be added to threadgroup
+ * and no existing live task will have its PF_EXITING set.
+ *
+ * During exec, a task goes and puts its thread group through unusual
+ * changes.  After de-threading, exclusive access is assumed to resources
+ * which are usually shared by tasks in the same group - e.g. sighand may
+ * be replaced with a new one.  Also, the exec'ing task takes over group
+ * leader role including its pid.  Exclude these changes while locked by
+ * grabbing cred_guard_mutex which is used to synchronize exec path.
+ */
+static inline void threadgroup_lock(struct task_struct *tsk)
 {
-	down_write(&tsk->signal->threadgroup_fork_lock);
+	/*
+	 * exec uses exit for de-threading nesting group_rwsem inside
+	 * cred_guard_mutex. Grab cred_guard_mutex first.
+	 */
+	mutex_lock(&tsk->signal->cred_guard_mutex);
+	down_write(&tsk->signal->group_rwsem);
 }
-static inline void threadgroup_fork_write_unlock(struct task_struct *tsk)
+
+/**
+ * threadgroup_unlock - unlock threadgroup
+ * @tsk: member task of the threadgroup to unlock
+ *
+ * Reverse threadgroup_lock().
+ */
+static inline void threadgroup_unlock(struct task_struct *tsk)
 {
-	up_write(&tsk->signal->threadgroup_fork_lock);
+	up_write(&tsk->signal->group_rwsem);
+	mutex_unlock(&tsk->signal->cred_guard_mutex);
 }
 #else
-static inline void threadgroup_fork_read_lock(struct task_struct *tsk) {}
-static inline void threadgroup_fork_read_unlock(struct task_struct *tsk) {}
-static inline void threadgroup_fork_write_lock(struct task_struct *tsk) {}
-static inline void threadgroup_fork_write_unlock(struct task_struct *tsk) {}
+static inline void threadgroup_change_begin(struct task_struct *tsk) {}
+static inline void threadgroup_change_end(struct task_struct *tsk) {}
+static inline void threadgroup_lock(struct task_struct *tsk) {}
+static inline void threadgroup_unlock(struct task_struct *tsk) {}
 #endif
 
 #ifndef __HAVE_THREAD_FUNCTIONS

kernel/cgroup_freezer.c

@@ -166,13 +166,17 @@ static bool is_task_frozen_enough(struct task_struct *task)
  */
 static int freezer_can_attach(struct cgroup_subsys *ss,
 			      struct cgroup *new_cgroup,
-			      struct task_struct *task)
+			      struct cgroup_taskset *tset)
 {
 	struct freezer *freezer;
+	struct task_struct *task;
 
 	/*
 	 * Anything frozen can't move or be moved to/from.
 	 */
+	cgroup_taskset_for_each(task, new_cgroup, tset)
+		if (cgroup_freezing(task))
+			return -EBUSY;
 
 	freezer = cgroup_freezer(new_cgroup);
 	if (freezer->state != CGROUP_THAWED)
@@ -181,11 +185,6 @@ static int freezer_can_attach(struct cgroup_subsys *ss,
 	return 0;
 }
 
-static int freezer_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
-{
-	return cgroup_freezing(tsk) ? -EBUSY : 0;
-}
-
 static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
 {
 	struct freezer *freezer;
@@ -381,10 +380,5 @@ 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,
 };

kernel/cpuset.c

@@ -1389,79 +1389,73 @@ static int fmeter_getrate(struct fmeter *fmp)
 	return val;
 }
 
-/* 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)
-{
-	struct cpuset *cs = cgroup_cs(cont);
-
-	if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
-		return -ENOSPC;
-
-	/*
-	 * Kthreads bound to specific cpus cannot be moved to a new cpuset; we
-	 * cannot change their cpu affinity and isolating such threads by their
-	 * set of allowed nodes is unnecessary.  Thus, cpusets are not
-	 * applicable for such threads.  This prevents checking for success of
-	 * set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may
-	 * be changed.
-	 */
-	if (tsk->flags & PF_THREAD_BOUND)
-		return -EINVAL;
-
-	return 0;
-}
-
-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.
+ * dynamically allocating them is not allowed in can_attach, and they must
+ * persist until 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)
+/* Called by cgroups to determine if a cpuset is usable; cgroup_mutex held */
+static int cpuset_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			     struct cgroup_taskset *tset)
 {
-	struct cpuset *cs = cgroup_cs(cont);
+	struct cpuset *cs = cgroup_cs(cgrp);
+	struct task_struct *task;
+	int ret;
 
+	if (cpumask_empty(cs->cpus_allowed) || nodes_empty(cs->mems_allowed))
+		return -ENOSPC;
+
+	cgroup_taskset_for_each(task, cgrp, tset) {
+		/*
+		 * Kthreads bound to specific cpus cannot be moved to a new
+		 * cpuset; we cannot change their cpu affinity and
+		 * isolating such threads by their set of allowed nodes is
+		 * unnecessary.  Thus, cpusets are not applicable for such
+		 * threads.  This prevents checking for success of
+		 * set_cpus_allowed_ptr() on all attached tasks before
+		 * cpus_allowed may be changed.
+		 */
+		if (task->flags & PF_THREAD_BOUND)
+			return -EINVAL;
+		if ((ret = security_task_setscheduler(task)))
+			return ret;
+	}
+
+	/* prepare for attach */
 	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);
+
+	return 0;
 }
 
-/* Per-thread attachment work. */
-static void cpuset_attach_task(struct cgroup *cont, struct task_struct *tsk)
+static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			  struct cgroup_taskset *tset)
 {
-	int err;
-	struct cpuset *cs = cgroup_cs(cont);
+	struct mm_struct *mm;
+	struct task_struct *task;
+	struct task_struct *leader = cgroup_taskset_first(tset);
+	struct cgroup *oldcgrp = cgroup_taskset_cur_cgroup(tset);
+	struct cpuset *cs = cgroup_cs(cgrp);
+	struct cpuset *oldcs = cgroup_cs(oldcgrp);
 
+	cgroup_taskset_for_each(task, cgrp, tset) {
 		/*
-	 * can_attach beforehand should guarantee that this doesn't fail.
-	 * TODO: have a better way to handle failure here
+		 * can_attach beforehand should guarantee that this doesn't
+		 * fail.  TODO: have a better way to handle failure here
 		 */
-	err = set_cpus_allowed_ptr(tsk, cpus_attach);
-	WARN_ON_ONCE(err);
-
-	cpuset_change_task_nodemask(tsk, &cpuset_attach_nodemask_to);
-	cpuset_update_task_spread_flag(cs, tsk);
-}
+		WARN_ON_ONCE(set_cpus_allowed_ptr(task, cpus_attach));
 
-static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
-			  struct cgroup *oldcont, struct task_struct *tsk)
-{
-	struct mm_struct *mm;
-	struct cpuset *cs = cgroup_cs(cont);
-	struct cpuset *oldcs = cgroup_cs(oldcont);
+		cpuset_change_task_nodemask(task, &cpuset_attach_nodemask_to);
+		cpuset_update_task_spread_flag(cs, task);
+	}
 
 	/*
 	 * Change mm, possibly for multiple threads in a threadgroup. This is
@@ -1469,7 +1463,7 @@ static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
 	 */
 	cpuset_attach_nodemask_from = oldcs->mems_allowed;
 	cpuset_attach_nodemask_to = cs->mems_allowed;
-	mm = get_task_mm(tsk);
+	mm = get_task_mm(leader);
 	if (mm) {
 		mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
 		if (is_memory_migrate(cs))
@@ -1925,9 +1919,6 @@ 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,

kernel/events/core.c

@@ -6941,9 +6941,12 @@ static int __perf_cgroup_move(void *info)
 	return 0;
 }
 
-static void
-perf_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *task)
+static void perf_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			       struct cgroup_taskset *tset)
 {
+	struct task_struct *task;
+
+	cgroup_taskset_for_each(task, cgrp, tset)
 		task_function_call(task, __perf_cgroup_move, task);
 }
 
@@ -6958,7 +6961,7 @@ static void perf_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
 	if (!(task->flags & PF_EXITING))
 		return;
 
-	perf_cgroup_attach_task(cgrp, task);
+	task_function_call(task, __perf_cgroup_move, task);
 }
 
 struct cgroup_subsys perf_subsys = {
@@ -6967,6 +6970,6 @@ struct cgroup_subsys perf_subsys = {
 	.create		= perf_cgroup_create,
 	.destroy	= perf_cgroup_destroy,
 	.exit		= perf_cgroup_exit,
-	.attach_task	= perf_cgroup_attach_task,
+	.attach		= perf_cgroup_attach,
 };
 #endif /* CONFIG_CGROUP_PERF */

kernel/fork.c

@@ -972,7 +972,7 @@ static int copy_signal(unsigned long clone_flags, struct task_struct *tsk)
 	sched_autogroup_fork(sig);
 
 #ifdef CONFIG_CGROUPS
-	init_rwsem(&sig->threadgroup_fork_lock);
+	init_rwsem(&sig->group_rwsem);
 #endif
 
 	sig->oom_adj = current->signal->oom_adj;
@@ -1153,7 +1153,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	p->io_context = NULL;
 	p->audit_context = NULL;
 	if (clone_flags & CLONE_THREAD)
-		threadgroup_fork_read_lock(current);
+		threadgroup_change_begin(current);
 	cgroup_fork(p);
 #ifdef CONFIG_NUMA
 	p->mempolicy = mpol_dup(p->mempolicy);
@@ -1368,7 +1368,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 	proc_fork_connector(p);
 	cgroup_post_fork(p);
 	if (clone_flags & CLONE_THREAD)
-		threadgroup_fork_read_unlock(current);
+		threadgroup_change_end(current);
 	perf_event_fork(p);
 	return p;
 
@@ -1403,7 +1403,7 @@ static struct task_struct *copy_process(unsigned long clone_flags,
 bad_fork_cleanup_cgroup:
 #endif
 	if (clone_flags & CLONE_THREAD)
-		threadgroup_fork_read_unlock(current);
+		threadgroup_change_end(current);
 	cgroup_exit(p, cgroup_callbacks_done);
 	delayacct_tsk_free(p);
 	module_put(task_thread_info(p)->exec_domain->module);

kernel/res_counter.c

@@ -159,8 +159,7 @@ int res_counter_memparse_write_strategy(const char *buf,
 		return 0;
 	}
 
-	/* FIXME - make memparse() take const char* args */
-	*res = memparse((char *)buf, &end);
+	*res = memparse(buf, &end);
 	if (*end != '\0')
 		return -EINVAL;
 

kernel/sched/core.c

@@ -7563,24 +7563,31 @@ cpu_cgroup_destroy(struct cgroup_subsys *ss, struct cgroup *cgrp)
 	sched_destroy_group(tg);
 }
 
-static int
-cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+static int cpu_cgroup_can_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+				 struct cgroup_taskset *tset)
 {
+	struct task_struct *task;
+
+	cgroup_taskset_for_each(task, cgrp, tset) {
 #ifdef CONFIG_RT_GROUP_SCHED
-	if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk))
+		if (!sched_rt_can_attach(cgroup_tg(cgrp), task))
 			return -EINVAL;
 #else
 		/* We don't support RT-tasks being in separate groups */
-	if (tsk->sched_class != &fair_sched_class)
+		if (task->sched_class != &fair_sched_class)
 			return -EINVAL;
 #endif
+	}
 	return 0;
 }
 
-static void
-cpu_cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
+static void cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
+			      struct cgroup_taskset *tset)
 {
-	sched_move_task(tsk);
+	struct task_struct *task;
+
+	cgroup_taskset_for_each(task, cgrp, tset)
+		sched_move_task(task);
 }
 
 static void
@@ -7915,8 +7922,8 @@ struct cgroup_subsys cpu_cgroup_subsys = {
 	.name		= "cpu",
 	.create		= cpu_cgroup_create,
 	.destroy	= cpu_cgroup_destroy,
-	.can_attach_task = cpu_cgroup_can_attach_task,
-	.attach_task	= cpu_cgroup_attach_task,
+	.can_attach	= cpu_cgroup_can_attach,
+	.attach		= cpu_cgroup_attach,
 	.exit		= cpu_cgroup_exit,
 	.populate	= cpu_cgroup_populate,
 	.subsys_id	= cpu_cgroup_subsys_id,

kernel/signal.c

@@ -2355,8 +2355,15 @@ void exit_signals(struct task_struct *tsk)
 	int group_stop = 0;
 	sigset_t unblocked;
 
+	/*
+	 * @tsk is about to have PF_EXITING set - lock out users which
+	 * expect stable threadgroup.
+	 */
+	threadgroup_change_begin(tsk);
+
 	if (thread_group_empty(tsk) || signal_group_exit(tsk->signal)) {
 		tsk->flags |= PF_EXITING;
+		threadgroup_change_end(tsk);
 		return;
 	}
 
@@ -2366,6 +2373,9 @@ void exit_signals(struct task_struct *tsk)
 	 * see wants_signal(), do_signal_stop().
 	 */
 	tsk->flags |= PF_EXITING;
+
+	threadgroup_change_end(tsk);
+
 	if (!signal_pending(tsk))
 		goto out;
 

mm/memcontrol.c

@@ -5391,8 +5391,9 @@ static void mem_cgroup_clear_mc(void)
 
 static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p)
+				struct cgroup_taskset *tset)
 {
+	struct task_struct *p = cgroup_taskset_first(tset);
 	int ret = 0;
 	struct mem_cgroup *memcg = mem_cgroup_from_cont(cgroup);
 
@@ -5430,7 +5431,7 @@ 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)
+				struct cgroup_taskset *tset)
 {
 	mem_cgroup_clear_mc();
 }
@@ -5547,9 +5548,9 @@ 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)
+				struct cgroup_taskset *tset)
 {
+	struct task_struct *p = cgroup_taskset_first(tset);
 	struct mm_struct *mm = get_task_mm(p);
 
 	if (mm) {
@@ -5564,19 +5565,18 @@ 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)
+				struct cgroup_taskset *tset)
 {
 	return 0;
 }
 static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p)
+				struct cgroup_taskset *tset)
 {
 }
 static void mem_cgroup_move_task(struct cgroup_subsys *ss,
 				struct cgroup *cont,
-				struct cgroup *old_cont,
-				struct task_struct *p)
+				struct cgroup_taskset *tset)
 {
 }
 #endif

security/device_cgroup.c

@@ -62,11 +62,12 @@ 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)
+			struct cgroup *new_cgrp, struct cgroup_taskset *set)
 {
+	struct task_struct *task = cgroup_taskset_first(set);
+
 	if (current != task && !capable(CAP_SYS_ADMIN))
 		return -EPERM;
-
 	return 0;
 }