Currently we just check for thread group leader in attach() handler but do
nothing! Either (1) move it to can_attach handler or (2) remove the test
itself. I am attaching patches for both below.
Thanks
Nikanth Karthikesan
Move thread group leader check to can_attach handler, but this may prevent non
thread group leaders to be moved at all!
Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
---
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 866dcc7..26bc823 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1136,6 +1136,18 @@ static int mem_cgroup_populate(struct cgroup_subsys
*ss,
ARRAY_SIZE(mem_cgroup_files));
}
+static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
+ struct cgroup *cgrp, struct task_struct *tsk)
+{
+ /*
+ * Only thread group leaders are allowed to migrate, the mm_struct is
+ * in effect owned by the leader
+ */
+ if (!thread_group_leader(tsk))
+ return -EINVAL;
+ return 0;
+}
+
static void mem_cgroup_move_task(struct cgroup_subsys *ss,
struct cgroup *cont,
struct cgroup *old_cont,
@@ -1151,14 +1163,6 @@ static void mem_cgroup_move_task(struct cgroup_subsys
*ss,
mem = mem_cgroup_from_cont(cont);
old_mem = mem_cgroup_from_cont(old_cont);
- /*
- * Only thread group leaders are allowed to migrate, the mm_struct is
- * in effect owned by the leader
- */
- if (!thread_group_leader(p))
- goto out;
-
-out:
mmput(mm);
}
@@ -1169,6 +1173,7 @@ struct cgroup_subsys mem_cgroup_subsys = {
.pre_destroy = mem_cgroup_pre_destroy,
.destroy = mem_cgroup_destroy,
.populate = mem_cgroup_populate,
+ .can_attach = mem_cgroup_can_attach,
.attach = mem_cgroup_move_task,
.early_init = 0,
};
The patch to remove unused code follows.
Remove the unused test for thread group leader.
Signed-off-by: Nikanth Karthikesan <knikanth@xxxxxxx>
---
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 866dcc7..8e9287d 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -1151,14 +1151,6 @@ static void mem_cgroup_move_task(struct cgroup_subsys
*ss,
mem = mem_cgroup_from_cont(cont);
old_mem = mem_cgroup_from_cont(old_cont);
- /*
- * Only thread group leaders are allowed to migrate, the mm_struct is
- * in effect owned by the leader
- */
- if (!thread_group_leader(p))
- goto out;
-
-out:
mmput(mm);
}
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