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Commit 494c167c authored by Tejun Heo's avatar Tejun Heo
Browse files

cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task() 



These three methods are no longer used.  Kill them.

Signed-off-by: default avatarTejun Heo <tj@kernel.org>
Reviewed-by: default avatarKAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Reviewed-by: default avatarFrederic Weisbecker <fweisbec@gmail.com>
Acked-by: default avatarPaul Menage <paul@paulmenage.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
parent 94196f51

Documentation/cgroups/cgroups.txt

+0 −20
Original line number Diff line number Diff line
@@ -615,13 +615,6 @@ 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 cgroup_taskset *tset)

(cgroup_mutex held by caller)
@@ -632,12 +625,6 @@ 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. The parameters are identical to can_attach().



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_taskset *tset)

(cgroup_mutex held by caller)
@@ -646,13 +633,6 @@ Called after the task has been attached to the cgroup, to allow any 
post-attachment activity that requires memory allocations or blocking.

The parameters are identical to can_attach().



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)



Called when a task is forked into a cgroup.

include/linux/cgroup.h

+0 −3
Original line number Diff line number Diff line
@@ -490,11 +490,8 @@ struct cgroup_subsys { 
	void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cgrp);

	int (*can_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,

			  struct cgroup_taskset *tset);

	int (*can_attach_task)(struct cgroup *cgrp, struct task_struct *tsk);

	void (*cancel_attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,

			      struct cgroup_taskset *tset);

	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_taskset *tset);

	void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);

kernel/cgroup.c

+5 −47
Original line number Diff line number Diff line
@@ -1944,13 +1944,6 @@ 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;

			}

		}

	}



	retval = cgroup_task_migrate(cgrp, oldcgrp, tsk, false);
@@ -1958,10 +1951,6 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) 
		goto out;



	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, &tset);

	}
@@ -2093,7 +2082,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
{

	int retval, i, group_size, nr_migrating_tasks;

	struct cgroup_subsys *ss, *failed_ss = NULL;

	bool cancel_failed_ss = false;

	/* guaranteed to be initialized later, but the compiler needs this */

	struct css_set *oldcg;

	struct cgroupfs_root *root = cgrp->root;
@@ -2188,21 +2176,6 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
				goto out_cancel_attach;

			}

		}

		/* a callback to be run on every thread in the threadgroup. */

		if (ss->can_attach_task) {

			/* run on each task in the threadgroup. */

			for (i = 0; i < group_size; i++) {

				tc = flex_array_get(group, i);

				if (tc->cgrp == cgrp)

					continue;

				retval = ss->can_attach_task(cgrp, tc->task);

				if (retval) {

					failed_ss = ss;

					cancel_failed_ss = true;

					goto out_cancel_attach;

				}

			}

		}

	}



	/*
@@ -2234,15 +2207,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
	}



	/*

	 * step 3: now that we're guaranteed success wrt the css_sets, proceed

	 * to move all tasks to the new cgroup, calling ss->attach_task for each

	 * one along the way. there are no failure cases after here, so this is

	 * the commit point.

	 * step 3: now that we're guaranteed success wrt the css_sets,

	 * proceed to move all tasks to the new cgroup.  There are no

	 * failure cases after here, so this is the commit point.

	 */

	for_each_subsys(root, ss) {

		if (ss->pre_attach)

			ss->pre_attach(cgrp);

	}

	for (i = 0; i < group_size; i++) {

		tc = flex_array_get(group, i);

		/* leave current thread as it is if it's already there */
@@ -2250,18 +2218,11 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
			continue;

		retval = cgroup_task_migrate(cgrp, tc->cgrp, tc->task, true);

		BUG_ON(retval);

		/* attach each task to each subsystem */

		for_each_subsys(root, ss) {

			if (ss->attach_task)

				ss->attach_task(cgrp, tc->task);

		}

	}

	/* nothing is sensitive to fork() after this point. */



	/*

	 * step 4: do expensive, non-thread-specific subsystem callbacks.

	 * TODO: if ever a subsystem needs to know the oldcgrp for each task

	 * being moved, this call will need to be reworked to communicate that.

	 * step 4: do subsystem attach callbacks.

	 */

	for_each_subsys(root, ss) {

		if (ss->attach)
@@ -2285,11 +2246,8 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader) 
	/* same deal as in cgroup_attach_task */

	if (retval) {

		for_each_subsys(root, ss) {

			if (ss == failed_ss) {

				if (cancel_failed_ss && ss->cancel_attach)

					ss->cancel_attach(ss, cgrp, &tset);

			if (ss == failed_ss)

				break;

			}

			if (ss->cancel_attach)

				ss->cancel_attach(ss, cgrp, &tset);

		}