Re: [RFC][PATCH 3/3] Process events biarch bug: New process events connector value

Chandra Seetharaman
2006-06-27T19:14:45Z

On Tue, 2006-06-27 at 04:49 -0700, Matt Helsley wrote:
> "Deprecate" existing Process Events connector interface and add a new one
> that works cleanly on biarch platforms.
>
> Any expansion of the previous event structure would break userspace's ability
> to workaround the biarch incompatibility problem. Hence this patch creates a
> new interface and generates events (for both when necessary).

Is there a reason why the # of listeners part is removed (basically the
LISTEN/IGNORE) ? and why as part of this patch ?

<snip>

> @@ -158,16 +164,15 @@ static int cn_proc_watch_task(struct not
> void *t)
> {
> struct task_struct *task = t;
> struct cn_msg *msg;
> struct proc_event *ev;
> + struct proc_event_deprecated *ev_old;
> + struct timespec timestamp;
> __u8 buffer[CN_PROC_MSG_SIZE];
> int rc = NOTIFY_OK;
>
> - if (atomic_read(&proc_event_num_listeners) < 1)
> - return rc;
> -
> msg = (struct cn_msg*)buffer;
> ev = (struct proc_event*)msg->data;
> switch (get_watch_event(val)) {
> case WATCH_TASK_CLONE:
> proc_fork_connector(task, ev);
> @@ -189,16 +194,26 @@ static int cn_proc_watch_task(struct not
> break;
> }
> if (rc != NOTIFY_OK)
> return rc;
> get_seq(&msg->seq, &ev->cpu);
> - ktime_get_ts(&ev->timestamp); /* get high res monotonic timestamp */
> + ktime_get_ts(&timestamp); /* get high res monotonic timestamp */
> + ev->timestamp_ns = ((__u64)timestamp.tv_sec*(__u64)NSEC_PER_SEC) + (__u64)timestamp.tv_nsec;
> memcpy(&msg->id, &cn_proc_event_id, sizeof(msg->id));
> msg->ack = 0; /* not used */
> msg->len = sizeof(*ev);
> cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
> /* If cn_netlink_send() fails, drop data */
> +
> + if (atomic_read(&proc_event_num_old_listeners) < 1)
> + return rc;
> + ev_old = (struct proc_event_deprecated*)msg->data;
> + msg->len = sizeof(*ev_old);

A comment saying the fields cpu, what, and ack are filled above and is
valid as is would help.

> + memmove(&ev_old->event_data, &ev->event_data, sizeof(ev->event_data));
> + memcpy(&ev_old->timestamp, &timestamp, sizeof(timestamp));
> + cn_netlink_send(msg, CN_IDX_PROC, GFP_KERNEL);
> + /* If cn_netlink_send() fails, drop data */
> return rc;
> }
>
> static struct notifier_block __read_mostly cn_proc_nb = {
> .notifier_call = cn_proc_watch_task,
> @@ -211,20 +226,27 @@ static struct notifier_block __read_most
> */
> static int __init cn_proc_init(void)
> {
> int err;
>
> - if ((err = cn_add_callback(&cn_proc_event_id, "cn_proc",
> - &cn_proc_mcast_ctl))) {
> - printk(KERN_WARNING "cn_proc failed to register\n");
> - goto out;
> - }
> + err = cn_add_callback(&cn_proc_event_deprecated_id, "cn_proc_old",
> + &cn_proc_mcast_old_ctl);
> + if (err)
> + goto error_old;

> + err = cn_add_callback(&cn_proc_event_id, "cn_proc", NULL);

is this needed if you are not going to have the callback ?

> + if (err)
> + goto error;
should not try to cn_del_callback(&cn_proc_event_id) ?! (goto error_old;
perhaps)

>
> err = register_task_watcher(&cn_proc_nb);
> - if (err != 0)
> - cn_del_callback(&cn_proc_event_id);
> -out:
> + if (err)
> + goto error;
> + return err;
> +error:
> + cn_del_callback(&cn_proc_event_id);
> +error_old:
> + cn_del_callback(&cn_proc_event_deprecated_id);
> + printk(KERN_WARNING "cn_proc failed to register\n");
> return err;
> }
>
<snip>
--

----------------------------------------------------------------------
Chandra Seetharaman | Be careful what you choose....
- sekharan@us.ibm.com | .......you may get it.
----------------------------------------------------------------------