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authorTejun Heo <tj@kernel.org>2013-08-08 20:11:23 -0400
committerTejun Heo <tj@kernel.org>2013-08-08 20:11:23 -0400
commiteb95419b023abacb415e2a18fea899023ce7624d (patch)
tree705284469b67cbe440b86c6cb81e1cf27648eba9 /kernel/cgroup_freezer.c
parent6387698699afd72d6304566fb6ccf84bffe07c56 (diff)
cgroup: pass around cgroup_subsys_state instead of cgroup in subsystem methods
cgroup is currently in the process of transitioning to using struct cgroup_subsys_state * as the primary handle instead of struct cgroup * in subsystem implementations for the following reasons. * With unified hierarchy, subsystems will be dynamically bound and unbound from cgroups and thus css's (cgroup_subsys_state) may be created and destroyed dynamically over the lifetime of a cgroup, which is different from the current state where all css's are allocated and destroyed together with the associated cgroup. This in turn means that cgroup_css() should be synchronized and may return NULL, making it more cumbersome to use. * Differing levels of per-subsystem granularity in the unified hierarchy means that the task and descendant iterators should behave differently depending on the specific subsystem the iteration is being performed for. * In majority of the cases, subsystems only care about its part in the cgroup hierarchy - ie. the hierarchy of css's. Subsystem methods often obtain the matching css pointer from the cgroup and don't bother with the cgroup pointer itself. Passing around css fits much better. This patch converts all cgroup_subsys methods to take @css instead of @cgroup. The conversions are mostly straight-forward. A few noteworthy changes are * ->css_alloc() now takes css of the parent cgroup rather than the pointer to the new cgroup as the css for the new cgroup doesn't exist yet. Knowing the parent css is enough for all the existing subsystems. * In kernel/cgroup.c::offline_css(), unnecessary open coded css dereference is replaced with local variable access. This patch shouldn't cause any behavior differences. v2: Unnecessary explicit cgrp->subsys[] deref in css_online() replaced with local variable @css as suggested by Li Zefan. Rebased on top of new for-3.12 which includes for-3.11-fixes so that ->css_free() invocation added by da0a12caff ("cgroup: fix a leak when percpu_ref_init() fails") is converted too. Suggested by Li Zefan. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com> Acked-by: Michal Hocko <mhocko@suse.cz> Acked-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Aristeu Rozanski <aris@redhat.com> Acked-by: Daniel Wagner <daniel.wagner@bmw-carit.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Balbir Singh <bsingharora@gmail.com> Cc: Matt Helsley <matthltc@us.ibm.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Steven Rostedt <rostedt@goodmis.org>
Diffstat (limited to 'kernel/cgroup_freezer.c')
-rw-r--r--kernel/cgroup_freezer.c40
1 files changed, 21 insertions, 19 deletions
diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
index 657a73cd44c4..f03a85719c3c 100644
--- a/kernel/cgroup_freezer.c
+++ b/kernel/cgroup_freezer.c
@@ -91,7 +91,8 @@ static const char *freezer_state_strs(unsigned int state)
struct cgroup_subsys freezer_subsys;
-static struct cgroup_subsys_state *freezer_css_alloc(struct cgroup *cgroup)
+static struct cgroup_subsys_state *
+freezer_css_alloc(struct cgroup_subsys_state *parent_css)
{
struct freezer *freezer;
@@ -104,16 +105,16 @@ static struct cgroup_subsys_state *freezer_css_alloc(struct cgroup *cgroup)
}
/**
- * freezer_css_online - commit creation of a freezer cgroup
- * @cgroup: cgroup being created
+ * freezer_css_online - commit creation of a freezer css
+ * @css: css being created
*
- * We're committing to creation of @cgroup. Mark it online and inherit
+ * We're committing to creation of @css. Mark it online and inherit
* parent's freezing state while holding both parent's and our
* freezer->lock.
*/
-static int freezer_css_online(struct cgroup *cgroup)
+static int freezer_css_online(struct cgroup_subsys_state *css)
{
- struct freezer *freezer = cgroup_freezer(cgroup);
+ struct freezer *freezer = css_freezer(css);
struct freezer *parent = parent_freezer(freezer);
/*
@@ -140,15 +141,15 @@ static int freezer_css_online(struct cgroup *cgroup)
}
/**
- * freezer_css_offline - initiate destruction of @cgroup
- * @cgroup: cgroup being destroyed
+ * freezer_css_offline - initiate destruction of a freezer css
+ * @css: css being destroyed
*
- * @cgroup is going away. Mark it dead and decrement system_freezing_count
- * if it was holding one.
+ * @css is going away. Mark it dead and decrement system_freezing_count if
+ * it was holding one.
*/
-static void freezer_css_offline(struct cgroup *cgroup)
+static void freezer_css_offline(struct cgroup_subsys_state *css)
{
- struct freezer *freezer = cgroup_freezer(cgroup);
+ struct freezer *freezer = css_freezer(css);
spin_lock_irq(&freezer->lock);
@@ -160,9 +161,9 @@ static void freezer_css_offline(struct cgroup *cgroup)
spin_unlock_irq(&freezer->lock);
}
-static void freezer_css_free(struct cgroup *cgroup)
+static void freezer_css_free(struct cgroup_subsys_state *css)
{
- kfree(cgroup_freezer(cgroup));
+ kfree(css_freezer(css));
}
/*
@@ -174,25 +175,26 @@ static void freezer_css_free(struct cgroup *cgroup)
* @freezer->lock. freezer_attach() makes the new tasks conform to the
* current state and all following state changes can see the new tasks.
*/
-static void freezer_attach(struct cgroup *new_cgrp, struct cgroup_taskset *tset)
+static void freezer_attach(struct cgroup_subsys_state *new_css,
+ struct cgroup_taskset *tset)
{
- struct freezer *freezer = cgroup_freezer(new_cgrp);
+ struct freezer *freezer = css_freezer(new_css);
struct task_struct *task;
bool clear_frozen = false;
spin_lock_irq(&freezer->lock);
/*
- * Make the new tasks conform to the current state of @new_cgrp.
+ * Make the new tasks conform to the current state of @new_css.
* For simplicity, when migrating any task to a FROZEN cgroup, we
* revert it to FREEZING and let update_if_frozen() determine the
* correct state later.
*
- * Tasks in @tset are on @new_cgrp but may not conform to its
+ * Tasks in @tset are on @new_css but may not conform to its
* current state before executing the following - !frozen tasks may
* be visible in a FROZEN cgroup and frozen tasks in a THAWED one.
*/
- cgroup_taskset_for_each(task, new_cgrp, tset) {
+ cgroup_taskset_for_each(task, new_css->cgroup, tset) {
if (!(freezer->state & CGROUP_FREEZING)) {
__thaw_task(task);
} else {