Re: [take12 3/3] kevent: Timer notifications.

Christoph Hellwig
2006-08-21T11:12:42Z

On Mon, Aug 21, 2006 at 02:19:49PM +0400, Evgeniy Polyakov wrote:
>
>
> Timer notifications.
>
> Timer notifications can be used for fine grained per-process time
> management, since interval timers are very inconvenient to use,
> and they are limited.

Shouldn't this at leat use a hrtimer?

> new file mode 100644
> index 0000000..5217cd1
> --- /dev/null
> +++ b/kernel/kevent/kevent_timer.c
> @@ -0,0 +1,107 @@
> +/*
> + * kevent_timer.c

You still include those sill filename ontop of file comments..

> +static struct lock_class_key kevent_timer_key;
> +
> +static int kevent_timer_enqueue(struct kevent *k)
> +{
> + int err;
> + struct kevent_timer *t;
> +
> + t = kmalloc(sizeof(struct kevent_timer), GFP_KERNEL);
> + if (!t)
> + return -ENOMEM;
> +
> + setup_timer(&t->ktimer, &kevent_timer_func, (unsigned long)k);
> +
> + err = kevent_storage_init(&t->ktimer, &t->ktimer_storage);
> + if (err)
> + goto err_out_free;
> + lockdep_set_class(&t->ktimer_storage.lock, &kevent_timer_key);

When looking at the kevent_storage_init callers most need to do
those lockdep_set_class class. Shouldn't kevent_storage_init just
get a "struct lock_class_key *" argument?

> +static int kevent_timer_callback(struct kevent *k)
> +{
> + k->event.ret_data[0] = (__u32)jiffies;

This is returned to userspace, isn't it? raw jiffies should never be
user-visible. Please convert this to an unit that actually makes sense
for userspace (probably nanoseconds)

> +static int __init kevent_init_timer(void)
> +{
> + struct kevent_callbacks tc = {
> + .callback = &kevent_timer_callback,
> + .enqueue = &kevent_timer_enqueue,
> + .dequeue = &kevent_timer_dequeue};

I think this should be static, and the normal style to write it would be:

static struct kevent_callbacks tc = {
.callback = kevent_timer_callback,
.enqueue = kevent_timer_enqueue,
.dequeue = kevent_timer_dequeue,
};

also please consider makring all the kevent_callbacks structs const
to avoid false cacheline sharing and accidental modification, similar
to what we did to various other operation vectors.