Home » Mailing lists » Devel » [PATCH] cgroup: Remove RCU from task->cgroups
| [PATCH 1/2] cgroup: Set CGRP_RELEASABLE when adding to a cgroup [message #41924 is a reply to message #41921] |
Wed, 24 November 2010 05:37   |
Colin Cross
Messages: 15
Registered: November 2010
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Junior Member |
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Changes the meaning of CGRP_RELEASABLE to be set on any cgroup
that has ever had a task or cgroup in it, or had css_get called
on it. The bit is set in cgroup_attach_task, cgroup_create,
and __css_get. It is not necessary to set the bit in
cgroup_fork, as the task is either in the root cgroup, in
which can never be released, or the task it was forked from
already set the bit in croup_attach_task.
Signed-off-by: Colin Cross <ccross@android.com>
---
include/linux/cgroup.h | 12 +--------
kernel/cgroup.c | 54 ++++++++++++++++++++---------------------------
2 files changed, 25 insertions(+), 41 deletions(-)
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ed4ba11..9e13078 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -84,12 +84,6 @@ enum {
CSS_REMOVED, /* This CSS is dead */
};
-/* Caller must verify that the css is not for root cgroup */
-static inline void __css_get(struct cgroup_subsys_state *css, int count)
-{
- atomic_add(count, &css->refcnt);
-}
-
/*
* Call css_get() to hold a reference on the css; it can be used
* for a reference obtained via:
@@ -97,6 +91,7 @@ static inline void __css_get(struct cgroup_subsys_state *css, int count)
* - task->cgroups for a locked task
*/
+extern void __css_get(struct cgroup_subsys_state *css, int count);
static inline void css_get(struct cgroup_subsys_state *css)
{
/* We don't need to reference count the root state */
@@ -143,10 +138,7 @@ static inline void css_put(struct cgroup_subsys_state *css)
enum {
/* Control Group is dead */
CGRP_REMOVED,
- /*
- * Control Group has previously had a child cgroup or a task,
- * but no longer (only if CGRP_NOTIFY_ON_RELEASE is set)
- */
+ /* Control Group has ever had a child cgroup or a task */
CGRP_RELEASABLE,
/* Control Group requires release notifications to userspace */
CGRP_NOTIFY_ON_RELEASE,
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 66a416b..34e855e 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -338,7 +338,15 @@ static void free_css_set_rcu(struct rcu_head *obj)
* compiled into their kernel but not actually in use */
static int use_task_css_set_links __read_mostly;
-static void __put_css_set(struct css_set *cg, int taskexit)
+/*
+ * refcounted get/put for css_set objects
+ */
+static inline void get_css_set(struct css_set *cg)
+{
+ atomic_inc(&cg->refcount);
+}
+
+static void put_css_set(struct css_set *cg)
{
struct cg_cgroup_link *link;
struct cg_cgroup_link *saved_link;
@@ -364,12 +372,8 @@ static void __put_css_set(struct css_set *cg, int taskexit)
struct cgroup *cgrp = link->cgrp;
list_del(&link->cg_link_list);
list_del(&link->cgrp_link_list);
- if (atomic_dec_and_test(&cgrp->count) &&
- notify_on_release(cgrp)) {
- if (taskexit)
- set_bit(CGRP_RELEASABLE, &cgrp->flags);
+ if (atomic_dec_and_test(&cgrp->count))
check_for_release(cgrp);
- }
kfree(link);
}
@@ -379,24 +383,6 @@ static void __put_css_set(struct css_set *cg, int taskexit)
}
/*
- * refcounted get/put for css_set objects
- */
-static inline void get_css_set(struct css_set *cg)
-{
- atomic_inc(&cg->refcount);
-}
-
-static inline void put_css_set(struct css_set *cg)
-{
- __put_css_set(cg, 0);
-}
-
-static inline void put_css_set_taskexit(struct css_set *cg)
-{
- __put_css_set(cg, 1);
-}
-
-/*
* compare_css_sets - helper function for find_existing_css_set().
* @cg: candidate css_set being tested
* @old_cg: existing css_set for a task
@@ -1801,7 +1787,7 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
if (ss->attach)
ss->attach(ss, cgrp, oldcgrp, tsk, false);
}
- set_bit(CGRP_RELEASABLE, &oldcgrp->flags);
+ set_bit(CGRP_RELEASABLE, &cgrp->flags);
synchronize_rcu();
put_css_set(cg);
@@ -3427,6 +3413,8 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
if (err < 0)
goto err_remove;
+ set_bit(CGRP_RELEASABLE, &parent->flags);
+
/* The cgroup directory was pre-locked for us */
BUG_ON(!mutex_is_locked(&cgrp->dentry->d_inode->i_mutex));
@@ -3645,7 +3633,6 @@ again:
cgroup_d_remove_dir(d);
dput(d);
- set_bit(CGRP_RELEASABLE, &parent->flags);
check_for_release(parent);
/*
@@ -4240,7 +4227,7 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
tsk->cgroups = &init_css_set;
task_unlock(tsk);
if (cg)
- put_css_set_taskexit(cg);
+ put_css_set(cg);
}
/**
@@ -4410,6 +4397,14 @@ static void check_for_release(struct cgroup *cgrp)
}
/* Caller must verify that the css is not for root cgroup */
+void __css_get(struct cgroup_subsys_state *css, int count)
+{
+ atomic_add(count, &css->refcnt);
+ set_bit(CGRP_RELEASABLE, &css->cgroup->flags);
+}
+EXPORT_SYMBOL_GPL(__css_get);
+
+/* Caller must verify that the css is not for root cgroup */
void __css_put(struct cgroup_subsys_state *css, int count)
{
struct cgroup *cgrp = css->cgroup;
@@ -4417,10 +4412,7 @@ void __css_put(struct cgroup_subsys_state *css, int count)
rcu_read_lock();
val = atomic_sub_return(count, &css->refcnt);
if (val == 1) {
- if (notify_on_release(cgrp)) {
- set_bit(CGRP_RELEASABLE, &cgrp->flags);
- check_for_release(cgrp);
- }
+ check_for_release(cgrp);
cgroup_wakeup_rmdir_waiter(cgrp);
}
rcu_read_unlock();
--
1.7.3.1
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