Re: [PATCH 3/6] cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach()

On Thu, 25 Aug 2011 10:20:49 +0200
Tejun Heo [off-list ref] wrote:

Hello, KAMEZAWA.

quoted

quoted

@@ -5460,8 +5460,9 @@ static void mem_cgroup_clear_mc(void)
 
 static int mem_cgroup_can_attach(struct cgroup_subsys *ss,
 				struct cgroup *cgroup,
-				struct task_struct *p)
+				struct cgroup_taskset *tset)
 {
+	struct task_struct *p = cgroup_taskset_first(tset);
 	int ret = 0;
 	struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup);
 

Ah..hmm. I think this doesn't work as expected for memcg.
Maybe code like this will be required.

Hmmm... the above is basically identity transformation of the existing
code.  If the above is broken, the current code is broken too.  Is it?

Current code is not broken.

mem_cgroup_can_attach(....., task) need to do real job only when task->mm->owner
== task. In this modification, you pass a set of task at once.
So, mem_cgroup_can_attach() need to check _all_ tasks in tset rather than a
first task in tset. please scan and find mm->owner.

Anyway, if you merge this onto mm-tree first, I think I can have time to
write a fix up if complicated.

Thanks,
-Kame