[RFC] cgroups: freezer -- Allow to attach a task to a frozen cgroup
From: Cyrill Gorcunov
Date: Mon Nov 28 2011 - 07:08:19 EST
In checkpoint/restore we need an ability to attach pids to
a frozen cgroup. Thus once pid reaches a frozen cgroup it is
not rejected, but the task get frozen immediately.
Signed-off-by: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
---
I would really appreciate complains and comments.
include/linux/cgroup.h | 2
kernel/cgroup.c | 6 +-
kernel/cgroup_freezer.c | 119 +++++++++++++++++++++++++++++++++---------------
mm/memcontrol.c | 2
4 files changed, 90 insertions(+), 39 deletions(-)
Index: linux-2.6.git/include/linux/cgroup.h
===================================================================
--- linux-2.6.git.orig/include/linux/cgroup.h
+++ linux-2.6.git/include/linux/cgroup.h
@@ -470,7 +470,7 @@ struct cgroup_subsys {
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);
+ struct cgroup *old_cgrp, 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,
Index: linux-2.6.git/kernel/cgroup.c
===================================================================
--- linux-2.6.git.orig/kernel/cgroup.c
+++ linux-2.6.git/kernel/cgroup.c
@@ -1884,7 +1884,7 @@ out:
*/
break;
if (ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, tsk);
+ ss->cancel_attach(ss, cgrp, oldcgrp, tsk);
}
}
return retval;
@@ -2178,11 +2178,11 @@ out_cancel_attach:
for_each_subsys(root, ss) {
if (ss == failed_ss) {
if (cancel_failed_ss && ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, leader);
+ ss->cancel_attach(ss, cgrp, oldcgrp, leader);
break;
}
if (ss->cancel_attach)
- ss->cancel_attach(ss, cgrp, leader);
+ ss->cancel_attach(ss, cgrp, oldcgrp, leader);
}
}
/* clean up the array of referenced threads in the group. */
Index: linux-2.6.git/kernel/cgroup_freezer.c
===================================================================
--- linux-2.6.git.orig/kernel/cgroup_freezer.c
+++ linux-2.6.git/kernel/cgroup_freezer.c
@@ -153,39 +153,6 @@ static void freezer_destroy(struct cgrou
kfree(cgroup_freezer(cgroup));
}
-/*
- * The call to cgroup_lock() in the freezer.state write method prevents
- * a write to that file racing against an attach, and hence the
- * can_attach() result will remain valid until the attach completes.
- */
-static int freezer_can_attach(struct cgroup_subsys *ss,
- struct cgroup *new_cgroup,
- struct task_struct *task)
-{
- struct freezer *freezer;
-
- /*
- * Anything frozen can't move or be moved to/from.
- */
-
- freezer = cgroup_freezer(new_cgroup);
- 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(tsk)) {
- rcu_read_unlock();
- return -EBUSY;
- }
- rcu_read_unlock();
- return 0;
-}
-
static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task)
{
struct freezer *freezer;
@@ -374,14 +341,96 @@ static int freezer_populate(struct cgrou
return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files));
}
+static int freezer_task_transition(struct task_struct *task, int state_to)
+{
+ int retval = 0;
+
+ switch (state_to) {
+ case CGROUP_THAWED:
+ thaw_process(task);
+ break;
+ case CGROUP_FROZEN:
+ case CGROUP_FREEZING:
+ if (freeze_task(task, true)) {
+ if (!frozen(task)) {
+ if (!freezing(task) &&
+ !freezer_should_skip(task))
+ retval = -EBUSY;
+ }
+ }
+ break;
+ }
+
+ return retval;
+}
+
+static int freezer_can_attach_task(struct cgroup *cgroup, struct task_struct *task)
+{
+ struct freezer *old_freezer;
+ struct freezer *freezer;
+
+ int goal_state, orig_state;
+ int retval = 0;
+
+ old_freezer = task_freezer(task);
+ freezer = cgroup_freezer(cgroup);
+
+ spin_lock_irq(&freezer->lock);
+
+ if (!spin_trylock_irq(&old_freezer->lock)) {
+ retval = -EBUSY;
+ goto out_unlock_freezer;
+ }
+
+ goal_state = orig_state = CGROUP_THAWED;
+
+ if (freezer->state == CGROUP_FREEZING ||
+ freezer->state == CGROUP_FROZEN)
+ goal_state = CGROUP_FREEZING;
+
+ if (old_freezer->state == CGROUP_FREEZING ||
+ old_freezer->state == CGROUP_FROZEN)
+ orig_state = CGROUP_FREEZING;
+
+ /* Nothing to change */
+ if (orig_state == goal_state)
+ goto done;
+
+ retval = freezer_task_transition(task, goal_state);
+done:
+ spin_unlock_irq(&old_freezer->lock);
+out_unlock_freezer:
+ spin_unlock_irq(&freezer->lock);
+
+ return retval;
+}
+
+static void freezer_cancel_attach(struct cgroup_subsys *ss,
+ struct cgroup *cgroup,
+ struct cgroup *old_cgroup,
+ struct task_struct *task)
+{
+ struct freezer *freezer = cgroup_freezer(old_cgroup);
+ int retval = 0;
+
+ spin_lock_irq(&freezer->lock);
+ retval = freezer_task_transition(task, freezer->state);
+ if (retval)
+ pr_warning("freezer: Can't move task (pid %d) to %s state\n",
+ task_pid_nr(task),
+ freezer_state_strs[freezer->state]);
+ spin_unlock_irq(&freezer->lock);
+}
+
struct cgroup_subsys freezer_subsys = {
.name = "freezer",
.create = freezer_create,
.destroy = freezer_destroy,
.populate = freezer_populate,
.subsys_id = freezer_subsys_id,
- .can_attach = freezer_can_attach,
- .can_attach_task = freezer_can_attach_task,
+ .can_attach = NULL,
+ .can_attach_task= freezer_can_attach_task,
+ .cancel_attach = freezer_cancel_attach,
.pre_attach = NULL,
.attach_task = NULL,
.attach = NULL,
Index: linux-2.6.git/mm/memcontrol.c
===================================================================
--- linux-2.6.git.orig/mm/memcontrol.c
+++ linux-2.6.git/mm/memcontrol.c
@@ -5337,6 +5337,7 @@ static int mem_cgroup_can_attach(struct
static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
+ struct cgroup *old_cgroup,
struct task_struct *p)
{
mem_cgroup_clear_mc();
@@ -5477,6 +5478,7 @@ static int mem_cgroup_can_attach(struct
}
static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss,
struct cgroup *cgroup,
+ struct cgroup *old_cgroup,
struct task_struct *p)
{
}
--
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