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Message-ID: <20111014003601.GC22527@ghc17.ghc.andrew.cmu.edu>
Date: Thu, 13 Oct 2011 20:36:01 -0400
From: Ben Blum <bblum@...rew.cmu.edu>
To: Andrew Morton <akpm@...ux-foundation.org>,
Oleg Nesterov <oleg@...hat.com>, linux-kernel@...r.kernel.org
Cc: Ben Blum <bblum@...rew.cmu.edu>, NeilBrown <neilb@...e.de>,
paulmck@...ux.vnet.ibm.com, Paul Menage <paul@...lmenage.org>,
Li Zefan <lizf@...fujitsu.com>,
containers@...ts.linux-foundation.org,
Frederic Weisbecker <fweisbec@...il.com>,
Balbir Singh <bsingharora@...il.com>,
Daisuke Nishimura <nishimura@....nes.nec.co.jp>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: [PATCH 2/2] cgroups: convert ss->attach to use whole threadgroup
flex_array (cpuset, memcontrol)
Convert ss->attach to take a flex_array of tasks instead of just the leader.
From: Ben Blum <bblum@...rew.cmu.edu>
This lets subsystems with whole-threadgroup attach calls (i.e., cpuset and
memcontrol) to accurately find the group's mm even when a non-leader does exec
and leaves the leader with a NULL mm pointer.
Also converts cpuset and memcontrol to take the flex_array and iterate down it
until an mm is found, instead of just attempting to use the leader's mm.
Signed-off-by: Ben Blum <bblum@...rew.cmu.edu>
---
Documentation/cgroups/cgroups.txt | 7 ++++++-
include/linux/cgroup.h | 4 +++-
kernel/cgroup.c | 16 +++++++++++++---
kernel/cpuset.c | 16 ++++++++++++++--
mm/memcontrol.c | 17 +++++++++++++++--
5 files changed, 51 insertions(+), 9 deletions(-)
diff --git a/Documentation/cgroups/cgroups.txt b/Documentation/cgroups/cgroups.txt
index 3fa646f..8e900ec 100644
--- a/Documentation/cgroups/cgroups.txt
+++ b/Documentation/cgroups/cgroups.txt
@@ -637,12 +637,17 @@ 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 *old_cgrp, struct task_struct *task)
+ struct cgroup *old_cgrp, struct flex_array *group,
+ int group_size)
(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.
+The flex_array contains pointers to every task_struct being moved, so
+that subsystems can, for example, iterate over a threadgroup's tasks to
+find one with an mm that needs to be moved.
+
void attach_task(struct cgroup *cgrp, struct cgroup *old_cgrp,
struct task_struct *tsk);
(cgroup_mutex held by caller)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ddc13eb..2f97a3b 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -25,6 +25,7 @@ struct cgroupfs_root;
struct inode;
struct cgroup;
struct css_id;
+struct flex_array;
extern int cgroup_init_early(void);
extern int cgroup_init(void);
@@ -481,7 +482,8 @@ struct cgroup_subsys {
void (*attach_task)(struct cgroup *cgrp, struct cgroup *old_cgrp,
struct task_struct *tsk);
void (*attach)(struct cgroup_subsys *ss, struct cgroup *cgrp,
- struct cgroup *old_cgrp, struct task_struct *tsk);
+ struct cgroup *old_cgrp, struct flex_array *group,
+ int group_size);
int (*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);
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 32fb4c8..f5fc882 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1824,10 +1824,18 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
struct cgroup *oldcgrp;
struct cgroupfs_root *root = cgrp->root;
+ /* Singleton array, for ss->attach (see cgroup_attach_proc). */
+ struct flex_array *group = flex_array_alloc(sizeof(tsk), 1, GFP_KERNEL);
+ if (!group)
+ return -ENOMEM;
+ retval = flex_array_put_ptr(group, 0, tsk, GFP_KERNEL);
+ if (retval < 0)
+ goto out_free_array;
+
/* Nothing to do if the task is already in that cgroup */
oldcgrp = task_cgroup_from_root(tsk, root);
if (cgrp == oldcgrp)
- return 0;
+ goto out_free_array;
for_each_subsys(root, ss) {
if (ss->can_attach) {
@@ -1862,7 +1870,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
if (ss->attach_task)
ss->attach_task(cgrp, oldcgrp, tsk);
if (ss->attach)
- ss->attach(ss, cgrp, oldcgrp, tsk);
+ ss->attach(ss, cgrp, oldcgrp, group, 1);
}
synchronize_rcu();
@@ -1890,6 +1898,8 @@ out:
ss->cancel_attach(ss, cgrp, tsk);
}
}
+out_free_array:
+ flex_array_free(group);
return retval;
}
@@ -2164,7 +2174,7 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
*/
for_each_subsys(root, ss) {
if (ss->attach)
- ss->attach(ss, cgrp, oldcgrp, leader);
+ ss->attach(ss, cgrp, oldcgrp, group, group_size);
}
/*
diff --git a/kernel/cpuset.c b/kernel/cpuset.c
index 00b3430..fce7841 100644
--- a/kernel/cpuset.c
+++ b/kernel/cpuset.c
@@ -59,6 +59,7 @@
#include <linux/mutex.h>
#include <linux/workqueue.h>
#include <linux/cgroup.h>
+#include <linux/flex_array.h>
/*
* Workqueue for cpuset related tasks.
@@ -1440,11 +1441,13 @@ static void cpuset_attach_task(struct cgroup *cont, struct cgroup *old,
}
static void cpuset_attach(struct cgroup_subsys *ss, struct cgroup *cont,
- struct cgroup *oldcont, struct task_struct *tsk)
+ struct cgroup *oldcont, struct flex_array *group,
+ int group_size)
{
struct mm_struct *mm;
struct cpuset *cs = cgroup_cs(cont);
struct cpuset *oldcs = cgroup_cs(oldcont);
+ int i;
/*
* Change mm, possibly for multiple threads in a threadgroup. This is
@@ -1452,7 +1455,16 @@ 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);
+ /*
+ * Find the first task in the group that still has its mm. (This could
+ * be not the first one if another did exec() and the leader exited.
+ */
+ for (i = 0; i < group_size; i++) {
+ struct task_struct *tsk = flex_array_get_ptr(group, i);
+ mm = get_task_mm(tsk);
+ if (mm)
+ break;
+ }
if (mm) {
mpol_rebind_mm(mm, &cpuset_attach_nodemask_to);
if (is_memory_migrate(cs))
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 6aff93c..f951a9c 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -49,6 +49,7 @@
#include <linux/page_cgroup.h>
#include <linux/cpu.h>
#include <linux/oom.h>
+#include <linux/flex_array.h>
#include "internal.h"
#include <asm/uaccess.h>
@@ -5455,9 +5456,21 @@ retry:
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct cgroup *cont,
struct cgroup *old_cont,
- struct task_struct *p)
+ struct flex_array *group, int group_size)
{
- struct mm_struct *mm = get_task_mm(p);
+ struct mm_struct *mm;
+ int i;
+
+ /*
+ * Find the first task in the group that still has its mm. (This could
+ * be not the first one if another did exec() and the leader exited.
+ */
+ for (i = 0; i < group_size; i++) {
+ struct task_struct *tsk = flex_array_get_ptr(group, i);
+ mm = get_task_mm(tsk);
+ if (mm)
+ break;
+ }
if (mm) {
if (mc.to)
--
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