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    SubjectRe: [RFC][PATCH] PM / Wakeup: Introduce wakeup source objects and event statistics (was: Re: Wakeup-events implementation)
    Date
    On Wednesday, September 08, 2010, Alan Stern wrote:
    > On Wed, 8 Sep 2010, Rafael J. Wysocki wrote:
    >
    > > Hi,
    > >
    > > Below is a patch that adds some statistics to the previously merged
    > > pm_wakeup_event()/pm_stay_awake()/pm_relax() code. It also makes it possible
    > > to use wakeup sources that are not directly associated with devices.
    >
    > I noted only a few things during a quick read-through.

    Great. :-)

    > See below.
    >
    > > It adds functions for manipulating wakeup source objects and reworks the
    > > device wakeup enabling/disabling to use the new functions. The list of wakeup
    > > sources is only used for updating the "hit count" statistics for now (this is
    > > the number of times the wakeup source was active when the PM core checked), but
    > > I'm planning to add a /proc file listing all wakeup sources, including the ones
    > > that are not attached to device objects.
    >
    > It must be obvious that this is starting to look more and more like the
    > suspend_blockers patch. What that means or will lead to, I don't
    > know...

    This actually is intentional, because I want to make it easier for the Android
    people to move their stuff towards the mainline, if they want to.

    > > It appears to work with the PCI wakeup code added previously, but that's only
    > > one case. I'm also not sure if it builds withoug CONFIG_PM_SLEEP. [BTW, I'm
    > > not sure it atomic_inc() and atomic_dec() imply a memory barrier in general.
    > > That seems to be the case on x86, but I don't know about other architectures.]
    >
    > They do not imply memory barriers. See the section on atomic
    > operations in Documentation/memory-barriers.txt.

    Ah. Thanks for the pointer.

    > > +/**
    > > + * wakeup_source_create - Create a struct wakeup_source object.
    > > + * @name: Name of the new wakeup source.
    > > + */
    > > +struct wakeup_source *wakeup_source_create(const char *name)
    > > +{
    > > + struct wakeup_source *ws;
    > > +
    > > + ws = kzalloc(sizeof(*ws), GFP_KERNEL);
    > > + if (!ws)
    > > + return NULL;
    > > +
    > > + if (name) {
    > > + int len = strlen(name);
    > > + char *s = kzalloc(len + 1, GFP_KERNEL);
    > > + if (s) {
    > > + strncpy(s, name, len);
    >
    > Would it be better to use kmalloc instead of kzalloc, call memcpy
    > instead of strncpy, and write the terminating NUL character manually?

    Yeah, thanks.

    > > + ws->name = s;
    > > + }
    > > + }
    > > +
    > > + return ws;
    > > +}
    > > +EXPORT_SYMBOL_GPL(wakeup_source_create);
    > > +
    > > +/**
    > > + * wakeup_source_destroy - Destroy a struct wakeup_source object.
    > > + * @ws: Wakeup source to destroy.
    > > + */
    > > +void wakeup_source_destroy(struct wakeup_source *ws)
    > > +{
    > > + if (!ws)
    > > + return;
    > > +
    > > + spin_lock_irq(&ws->lock);
    >
    > Since you use the spinlock here, it needs to be initialized in
    > wakeup_source_create rather than wakeup_source_register.

    Yes, thanks.

    > > + while (ws->active) {
    > > + spin_unlock_irq(&ws->lock);
    > > +
    > > + schedule_timeout_interruptible(msecs_to_jiffies(TIMEOUT));
    > > +
    > > + spin_lock_irq(&ws->lock);
    > > + }
    > > + spin_unlock_irq(&ws->lock);
    > > +
    > > + if (ws->name)
    > > + kfree(ws->name);
    >
    > No need for the "if".

    OK

    > > + kfree(ws);
    > > +}
    > > +EXPORT_SYMBOL_GPL(wakeup_source_destroy);
    > > +
    > > +/**
    > > + * wakeup_source_register - Add given object to the list of wakeup sources.
    > > + * @ws: Wakeup source object to register.
    > > + */
    > > +void wakeup_source_register(struct wakeup_source *ws)
    > > +{
    > > + if (WARN_ON(!ws))
    > > + return;
    > > +
    > > + spin_lock_init(&ws->lock);
    > > + setup_timer(&ws->timer, pm_wakeup_timer_fn, (unsigned long)ws);
    > > + ws->active = false;
    > > +
    > > + spin_lock_irq(&events_lock);
    > > + list_add_rcu(&ws->entry, &wakeup_sources);
    > > + spin_unlock_irq(&events_lock);
    > > + synchronize_rcu();
    > > +}
    > > +EXPORT_SYMBOL_GPL(wakeup_source_register);
    >
    > ...
    >
    > > +/**
    > > + * wakeup_source_add - Create and register a wakeup source object.
    > > + * @name: Name of the wakeup source to create.
    > > + */
    > > +struct wakeup_source *wakeup_source_add(const char *name)
    > > +{
    > > + struct wakeup_source *ws;
    > > +
    > > + ws = wakeup_source_create(name);
    > > + if (ws)
    > > + wakeup_source_register(ws);
    > > +
    > > + return ws;
    > > +}
    > > +EXPORT_SYMBOL_GPL(wakeup_source_add);
    >
    > Your use of names is backward. Normally the *_register routine does
    > *_init followed by *_add.

    Hmm, I haven't noticed that. Thanks for the heads up. :-)

    > I haven't looked through the rest in enough detail yet to make any
    > meaningful comments.

    Sure. Thanks a lot for your comments so far!

    Rafael


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