Re: [RFC] Add mempressure cgroup

On Wed, Nov 28, 2012 at 02:29:08AM -0800, Anton Vorontsov wrote:

+static int mpc_pre_destroy(struct cgroup *cg) +{

• struct mpc_state *mpc = cg2mpc(cg);
• int ret = 0;
• mutex_lock(&mpc->lock);
• if (mpc->eventfd)

• ret = -EBUSY;
  

cgroup_rmdir() will unregister all events for you. No need to handle it here.

• mutex_unlock(&mpc->lock);
• return ret;

+}

+static int mpc_register_level_event(struct cgroup *cg, struct cftype *cft,

• 		    struct eventfd_ctx *eventfd,
  

• 		    const char *args)
  

+{

• struct mpc_state *mpc = cg2mpc(cg);
• int i;
• int ret;
• mutex_lock(&mpc->lock);
• /*

• * It's easy to implement multiple thresholds, but so far we don't
  

• * need it.
  

• */
  

• if (mpc->eventfd) {

• ret = -EBUSY;
  

• goto out_unlock;
  

• }

One user which listen for one threashold per cgroup? I think it's wrong. It's essensial for API to serve multiple users.

• ret = -EINVAL;
• for (i = 0; i < VMPRESSURE_NUM_LEVELS; i++) {

• if (strcmp(vmpressure_str_levels[i], args))
  

• 	continue;
  

• mpc->eventfd = eventfd;
  

• mpc->thres = i;
  

• ret = 0;
  

• break;
  

• }

+out_unlock:

• mutex_unlock(&mpc->lock);
• return ret;

+}