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Re: [RFC v1 08/14] bus1: implement peer management context

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  Re: [RFC v1 08/14] bus1: implement peer management context Richard Weinberger <richard.weinberger@gmail.com> - 2016-10-28 15:10 +0200
    Re: [RFC v1 08/14] bus1: implement peer management context Tom Gundersen <teg@jklm.no> - 2016-10-28 15:30 +0200
      Re: [RFC v1 08/14] bus1: implement peer management context Richard Weinberger <richard@nod.at> - 2016-10-28 16:00 +0200

#1511121 — Re: [RFC v1 08/14] bus1: implement peer management context

On Wed, Oct 26, 2016 at 9:18 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
> +       /* initialize constant fields */
> +       peer->id = atomic64_inc_return(&peer_ids);
> +       peer->flags = 0;
> +       peer->cred = get_cred(current_cred());
> +       peer->pid_ns = get_pid_ns(task_active_pid_ns(current));
> +       peer->user = user;
> +       peer->debugdir = NULL;
> +       init_waitqueue_head(&peer->waitq);
> +       bus1_active_init(&peer->active);
> +
> +       /* initialize data section */
> +       mutex_init(&peer->data.lock);
> +
> +       /* initialize peer-private section */
> +       mutex_init(&peer->local.lock);
> +
> +       if (!IS_ERR_OR_NULL(bus1_debugdir)) {

How can bus1_debugdir contain an error code? AFACT it is either a
valid dentry or NULL.

> +               char idstr[22];
> +
> +               snprintf(idstr, sizeof(idstr), "peer-%llx", peer->id);
> +
> +               peer->debugdir = debugfs_create_dir(idstr, bus1_debugdir);
> +               if (!peer->debugdir) {
> +                       pr_err("cannot create debugfs dir for peer %llx\n",
> +                              peer->id);
> +               } else if (!IS_ERR_OR_NULL(peer->debugdir)) {
> +                       bus1_debugfs_create_atomic_x("active", S_IRUGO,
> +                                                    peer->debugdir,
> +                                                    &peer->active.count);
> +               }
> +       }
> +
> +       bus1_active_activate(&peer->active);

This is a no-nop since bus1_active_init() set ->count to BUS1_ACTIVE_NEW.

> +       return peer;
> +}
> +
> +static int bus1_peer_disconnect(struct bus1_peer *peer)
> +{
> +       bus1_active_deactivate(&peer->active);
> +       bus1_active_drain(&peer->active, &peer->waitq);
> +
> +       if (!bus1_active_cleanup(&peer->active, &peer->waitq,
> +                                NULL, NULL))
> +               return -ESHUTDOWN;
> +
> +       return 0;
> +}
> +
> +/**
> + * bus1_peer_free() - destroy peer
> + * @peer:      peer to destroy, or NULL
> + *
> + * Destroy a peer object that was previously allocated via bus1_peer_new().
> + * This synchronously waits for any outstanding operations on this peer to
> + * finish, then releases all linked resources and deallocates the peer in an
> + * rcu-delayed manner.
> + *
> + * If NULL is passed, this is a no-op.
> + *
> + * Return: NULL is returned.

What about making the function of type void?

> +struct bus1_peer *bus1_peer_free(struct bus1_peer *peer)
> +{
> +       if (!peer)
> +               return NULL;
> +
> +       /* disconnect from environment */
> +       bus1_peer_disconnect(peer);
> +
> +       /* deinitialize peer-private section */
> +       mutex_destroy(&peer->local.lock);
> +
> +       /* deinitialize data section */
> +       mutex_destroy(&peer->data.lock);
> +
> +       /* deinitialize constant fields */
> +       debugfs_remove_recursive(peer->debugdir);
> +       bus1_active_deinit(&peer->active);
> +       peer->user = bus1_user_unref(peer->user);
> +       put_pid_ns(peer->pid_ns);
> +       put_cred(peer->cred);
> +       kfree_rcu(peer, rcu);
> +
> +       return NULL;
> +}

-- 
Thanks,
//richard

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#1511126

On Fri, Oct 28, 2016 at 3:05 PM, Richard Weinberger
<richard.weinberger@gmail.com> wrote:
> On Wed, Oct 26, 2016 at 9:18 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
>> +       /* initialize constant fields */
>> +       peer->id = atomic64_inc_return(&peer_ids);
>> +       peer->flags = 0;
>> +       peer->cred = get_cred(current_cred());
>> +       peer->pid_ns = get_pid_ns(task_active_pid_ns(current));
>> +       peer->user = user;
>> +       peer->debugdir = NULL;
>> +       init_waitqueue_head(&peer->waitq);
>> +       bus1_active_init(&peer->active);
>> +
>> +       /* initialize data section */
>> +       mutex_init(&peer->data.lock);
>> +
>> +       /* initialize peer-private section */
>> +       mutex_init(&peer->local.lock);
>> +
>> +       if (!IS_ERR_OR_NULL(bus1_debugdir)) {
>
> How can bus1_debugdir contain an error code? AFACT it is either a
> valid dentry or NULL.

If debugfs is not enabled it will be ERR_PTR(-ENODEV).

>> +               char idstr[22];
>> +
>> +               snprintf(idstr, sizeof(idstr), "peer-%llx", peer->id);
>> +
>> +               peer->debugdir = debugfs_create_dir(idstr, bus1_debugdir);
>> +               if (!peer->debugdir) {
>> +                       pr_err("cannot create debugfs dir for peer %llx\n",
>> +                              peer->id);
>> +               } else if (!IS_ERR_OR_NULL(peer->debugdir)) {
>> +                       bus1_debugfs_create_atomic_x("active", S_IRUGO,
>> +                                                    peer->debugdir,
>> +                                                    &peer->active.count);
>> +               }
>> +       }
>> +
>> +       bus1_active_activate(&peer->active);
>
> This is a no-nop since bus1_active_init() set ->count to BUS1_ACTIVE_NEW.

bus1_active_activate() changes count from BUS1_ACTIVE_NEW to 0.

>> +       return peer;
>> +}
>> +
>> +static int bus1_peer_disconnect(struct bus1_peer *peer)
>> +{
>> +       bus1_active_deactivate(&peer->active);
>> +       bus1_active_drain(&peer->active, &peer->waitq);
>> +
>> +       if (!bus1_active_cleanup(&peer->active, &peer->waitq,
>> +                                NULL, NULL))
>> +               return -ESHUTDOWN;
>> +
>> +       return 0;
>> +}
>> +
>> +/**
>> + * bus1_peer_free() - destroy peer
>> + * @peer:      peer to destroy, or NULL
>> + *
>> + * Destroy a peer object that was previously allocated via bus1_peer_new().
>> + * This synchronously waits for any outstanding operations on this peer to
>> + * finish, then releases all linked resources and deallocates the peer in an
>> + * rcu-delayed manner.
>> + *
>> + * If NULL is passed, this is a no-op.
>> + *
>> + * Return: NULL is returned.
>
> What about making the function of type void?

We are consistently returning the type being freed so we can do

foo->bar = bar_free(bar);

Just a matter of style though.

>> +struct bus1_peer *bus1_peer_free(struct bus1_peer *peer)
>> +{
>> +       if (!peer)
>> +               return NULL;
>> +
>> +       /* disconnect from environment */
>> +       bus1_peer_disconnect(peer);
>> +
>> +       /* deinitialize peer-private section */
>> +       mutex_destroy(&peer->local.lock);
>> +
>> +       /* deinitialize data section */
>> +       mutex_destroy(&peer->data.lock);
>> +
>> +       /* deinitialize constant fields */
>> +       debugfs_remove_recursive(peer->debugdir);
>> +       bus1_active_deinit(&peer->active);
>> +       peer->user = bus1_user_unref(peer->user);
>> +       put_pid_ns(peer->pid_ns);
>> +       put_cred(peer->cred);
>> +       kfree_rcu(peer, rcu);
>> +
>> +       return NULL;
>> +}
>
> --
> Thanks,
> //richard

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#1511143

On 28.10.2016 15:23, Tom Gundersen wrote:
> On Fri, Oct 28, 2016 at 3:05 PM, Richard Weinberger
> <richard.weinberger@gmail.com> wrote:
>> On Wed, Oct 26, 2016 at 9:18 PM, David Herrmann <dh.herrmann@gmail.com> wrote:
>>> +       /* initialize constant fields */
>>> +       peer->id = atomic64_inc_return(&peer_ids);
>>> +       peer->flags = 0;
>>> +       peer->cred = get_cred(current_cred());
>>> +       peer->pid_ns = get_pid_ns(task_active_pid_ns(current));
>>> +       peer->user = user;
>>> +       peer->debugdir = NULL;
>>> +       init_waitqueue_head(&peer->waitq);
>>> +       bus1_active_init(&peer->active);
>>> +
>>> +       /* initialize data section */
>>> +       mutex_init(&peer->data.lock);
>>> +
>>> +       /* initialize peer-private section */
>>> +       mutex_init(&peer->local.lock);
>>> +
>>> +       if (!IS_ERR_OR_NULL(bus1_debugdir)) {
>>
>> How can bus1_debugdir contain an error code? AFACT it is either a
>> valid dentry or NULL.
> 
> If debugfs is not enabled it will be ERR_PTR(-ENODEV).

I thought you handle that earlier. But just figured that you check only
for NULL after doing debugfs_create_dir(). This confused me.

>>> +               char idstr[22];
>>> +
>>> +               snprintf(idstr, sizeof(idstr), "peer-%llx", peer->id);
>>> +
>>> +               peer->debugdir = debugfs_create_dir(idstr, bus1_debugdir);
>>> +               if (!peer->debugdir) {
>>> +                       pr_err("cannot create debugfs dir for peer %llx\n",
>>> +                              peer->id);
>>> +               } else if (!IS_ERR_OR_NULL(peer->debugdir)) {
>>> +                       bus1_debugfs_create_atomic_x("active", S_IRUGO,
>>> +                                                    peer->debugdir,
>>> +                                                    &peer->active.count);
>>> +               }
>>> +       }
>>> +
>>> +       bus1_active_activate(&peer->active);
>>
>> This is a no-nop since bus1_active_init() set ->count to BUS1_ACTIVE_NEW.
> 
> bus1_active_activate() changes count from BUS1_ACTIVE_NEW to 0.

Too many "active" words. ;)
Now it makes sense. BUS1_ACTIVE_NEW is state "NEW"
and the unnamed state "ready to use" is a counter >= 0.

Thanks,
//richard

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