cgroup: Fix cgroup_subsys::exit callback

Make the ::exit method act like ::attach, it is after all very nearly
the same thing.

The bug had no effect on correctness - fixing it is an optimization for
the scheduler. Also, later perf-cgroups patches rely on it.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Acked-by: Paul Menage <menage@google.com>
LKML-Reference: <1297160655.13327.92.camel@laptop>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index ce104e3..38117d9 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -474,7 +474,8 @@ struct cgroup_subsys {
                        struct cgroup *old_cgrp, struct task_struct *tsk,
                        bool threadgroup);
        void (*fork)(struct cgroup_subsys *ss, struct task_struct *task);
-       void (*exit)(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);
        int (*populate)(struct cgroup_subsys *ss,
                        struct cgroup *cgrp);
        void (*post_clone)(struct cgroup_subsys *ss, struct cgroup *cgrp);

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b24d702..f6495f3 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -4230,20 +4230,8 @@ void cgroup_post_fork(struct task_struct *child)
  */
 void cgroup_exit(struct task_struct *tsk, int run_callbacks)
 {
-       int i;
        struct css_set *cg;
-
-       if (run_callbacks && need_forkexit_callback) {
-               /*
-                * modular subsystems can't use callbacks, so no need to lock
-                * the subsys array
-                */
-               for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
-                       struct cgroup_subsys *ss = subsys[i];
-                       if (ss->exit)
-                               ss->exit(ss, tsk);
-               }
-       }
+       int i;
 
        /*
         * Unlink from the css_set task list if necessary.
@@ -4261,7 +4249,24 @@ void cgroup_exit(struct task_struct *tsk, int run_callbacks)
        task_lock(tsk);
        cg = tsk->cgroups;
        tsk->cgroups = &init_css_set;
+
+       if (run_callbacks && need_forkexit_callback) {
+               /*
+                * modular subsystems can't use callbacks, so no need to lock
+                * the subsys array
+                */
+               for (i = 0; i < CGROUP_BUILTIN_SUBSYS_COUNT; i++) {
+                       struct cgroup_subsys *ss = subsys[i];
+                       if (ss->exit) {
+                               struct cgroup *old_cgrp =
+                                       rcu_dereference_raw(cg->subsys[i])->cgroup;
+                               struct cgroup *cgrp = task_cgroup(tsk, i);
+                               ss->exit(ss, cgrp, old_cgrp, tsk);
+                       }
+               }
+       }
        task_unlock(tsk);
+
        if (cg)
                put_css_set_taskexit(cg);
 }

diff --git a/kernel/sched.c b/kernel/sched.c
index e142e92..79e611c 100644 (file)
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -606,9 +606,6 @@ static inline struct task_group *task_group(struct task_struct *p)
        struct task_group *tg;
        struct cgroup_subsys_state *css;
 
-       if (p->flags & PF_EXITING)
-               return &root_task_group;
-
        css = task_subsys_state_check(p, cpu_cgroup_subsys_id,
                        lockdep_is_held(&task_rq(p)->lock));
        tg = container_of(css, struct task_group, css);
@@ -8863,7 +8860,8 @@ cpu_cgroup_attach(struct cgroup_subsys *ss, struct cgroup *cgrp,
 }
 
 static void
-cpu_cgroup_exit(struct cgroup_subsys *ss, struct task_struct *task)
+cpu_cgroup_exit(struct cgroup_subsys *ss, struct cgroup *cgrp,
+               struct cgroup *old_cgrp, struct task_struct *task)
 {
        /*
         * cgroup_exit() is called in the copy_process() failure path.