On Mon, 24 Mar 2008, Rafael J. Wysocki wrote:
> Hi,
>
> This is the 3rd revision of the patch introducing new callbacks for suspend
> and hibernation. It has been tested on x86-64.
...
> * The registrations of parentless devices are disabled before the first
> ->prepare() method is called and enabled before the first ->resume() method
> is called
It would be okay to wait until after the last prepare() method is
called. I don't know if it makes any difference in the end, however.
> +enum dpm_state {
> + DPM_ON,
> + DPM_RESUMING,
> + DPM_SUSPENDING,
> + DPM_OFF,
> + DPM_OFF_IRQ,
> +};
Can we also have a DPM_PREPARING state, set when ->prepare() is about
to be called? The PM core wouldn't make use of it but some drivers
would. (I can't think of any use at all for the analogous
DPM_COMPLETING state, however.)
> @@ -68,22 +59,30 @@ int device_pm_add(struct device *dev)
...
> + if (dev->parent) {
> + if (dev->parent->power.status > DPM_RESUMING) {
Clearer to say: if (dev->parent->power.status >= DPM_SUSPENDING) {
...
> + } else if (transition_started) {
> + /*
> + * We refuse to register parentless devices while a PM
> + * transition is in progress in order to avoid leaving them
> + * unhandled down the road
> + */
Log a warning here? If this ever happened, it would be the sort of
unexpected regression that people get all excited about.
> + goto Refuse;
> }
...
> +static void dpm_resume(pm_message_t state)
> +{
> + struct list_head list;
> +
> + INIT_LIST_HEAD(&list);
> + mutex_lock(&dpm_list_mtx);
> + transition_started = false;
> + while (!list_empty(&dpm_list)) {
> + struct device *dev = to_device(dpm_list.next);
> +
> + if (dev->power.status > DPM_SUSPENDING) {
Clearer to say: if (dev->power.status >= DPM_OFF) {
Note that if dev->power.status is equal to DPM_SUSPENDING then you
don't want to call resume_device(), but you still do want to change
dev->power.status to DPM_RESUMING so that new children can be
registered.
> + dev->power.status = DPM_RESUMING;
> + get_device(dev);
> + mutex_unlock(&dpm_list_mtx);
> +
> + resume_device(dev, state);
> +
> + mutex_lock(&dpm_list_mtx);
> + put_device(dev);
> + }
> + if (!list_empty(&dev->power.entry))
> + list_move_tail(&dev->power.entry, &list);
A little problem here: You refer to dev after calling put_device().
> + }
> + list_splice(&list, &dpm_list);
This isn't the way I imagined doing it (your extra "list"), but it's
fine.
...
> +static void dpm_complete(pm_message_t state)
> {
...
> + complete_device(dev, state);
> +
> + mutex_lock(&dpm_list_mtx);
> + put_device(dev);
> + }
> + if (!list_empty(&dev->power.entry))
> + list_move(&dev->power.entry, &list);
Same problem with use-after-put. Also present in dpm_prepare().
> }
> + list_splice(&list, &dpm_list);
> mutex_unlock(&dpm_list_mtx);
> }
...
> static int dpm_suspend(pm_message_t state)
> {
...
> error = suspend_device(dev, state);
> +
> mutex_lock(&dpm_list_mtx);
> + put_device(dev);
> if (error) {
> printk(KERN_ERR "Could not suspend device %s: "
> - "error %d%s\n",
> - kobject_name(&dev->kobj),
> - error,
> - (error == -EAGAIN ?
> - " (please convert to suspend_late)" :
> - ""));
> - dev->power.sleeping = false;
> + "error %d\n", kobject_name(&dev->kobj), error);
> + list_splice_init(&dpm_list, &list);
> break;
> }
> - if (!list_empty(&dev->power.entry))
> - list_move(&dev->power.entry, &dpm_off);
> + if (!list_empty(&dev->power.entry)) {
> + dev->power.status = DPM_OFF;
> + list_move(&dev->power.entry, &list);
> + }
Use-after-put again.
> }
> - if (!error)
> - all_sleeping = true;
> + list_splice(&list, &dpm_list);
Instead you could eliminate the list_splice_init() above and put here:
list_splice(&list, dpm_list->prev);
This will move the entries from list to the end of dpm_list.
> mutex_unlock(&dpm_list_mtx);
> + return error;
> +}
On the whole it looks quite good.
Alan Stern
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