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    SubjectRe: [RFC][PATCH 0/8] PM: Implement autosleep and "wake locks"
    Date
    On Thursday, February 16, 2012, Rafael J. Wysocki wrote:
    > On Wednesday, February 15, 2012, Arve Hjønnevåg wrote:
    > > 2012/2/14 Rafael J. Wysocki <rjw@sisk.pl>:
    > > > On Tuesday, February 14, 2012, Arve Hjønnevåg wrote:
    > > >> On Mon, Feb 6, 2012 at 5:00 PM, Rafael J. Wysocki <rjw@sisk.pl> wrote:
    > > >> ...
    > > >> but the wake-source timeout feature has some bugs or incompatible apis. An
    > > >> init api would also be useful for embedding wake-sources in other data
    > > >> structures without adding another memory allocation. Your patch to
    > > >> move the spinlock init to wakeup_source_add still require the struct
    > > >> to be zero initialized and the name set manually.
    > > >
    > > > That should be easy to fix. What about the appended patch?
    > > >
    > >
    > > That works, but I still have to call more than one function before I
    > > can use the wakeup-source (wakeup_source_init and wakeup_source_add)
    > > and more than one function before I can free it (__pm_relax,
    > > wakeup_source_remove and wakeup_source_drop). Is there any reason to
    > > keep these separate?
    >
    > Yes, there is. I think that wakeup_source_create/_destroy() should
    > use the same initialization functions internally that will be used for
    > externally allocated wakeup sources (to make sure that all wakeup source
    > objects are initialized in exactly the same way).
    >
    > > Also, not copying the name when the caller provides the memory for the
    > > wakeup-source would be a closer match to the wakelock api. Most of our
    > > wakelocks pass a string constant as the name, and making a copy of
    > > that string is not useful. wake_lock_init is also safe to call from
    > > atomic context, but I don't know if anyone relies on this.
    >
    > OK, below is another go. It doesn't copy the name if wakeup_source_init() is
    > used (which also does the _add this time). I think, though, that copying
    > the name is generally safer, because someone might use wakeup_source_init()
    > with the name string allocated on the stack or otherwise temporary, which would
    > be a bug with the new version.

    So, is the new version more suitable than the previous one?

    Rafael


    > Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
    > ---
    > drivers/base/power/wakeup.c | 41 ++++++++++++++++++++++++++++++++++-------
    > include/linux/pm_wakeup.h | 20 ++++++++++++++++++++
    > 2 files changed, 54 insertions(+), 7 deletions(-)
    >
    > Index: linux/drivers/base/power/wakeup.c
    > ===================================================================
    > --- linux.orig/drivers/base/power/wakeup.c
    > +++ linux/drivers/base/power/wakeup.c
    > @@ -53,6 +53,23 @@ static void pm_wakeup_timer_fn(unsigned
    > static LIST_HEAD(wakeup_sources);
    >
    > /**
    > + * wakeup_source_prepare - Prepare a new wakeup source for initialization.
    > + * @ws: Wakeup source to prepare.
    > + * @name: Pointer to the name of the new wakeup source.
    > + *
    > + * Callers must ensure that the @name string won't be freed when @ws is still in
    > + * use.
    > + */
    > +void wakeup_source_prepare(struct wakeup_source *ws, const char *name)
    > +{
    > + if (ws) {
    > + memset(ws, 0, sizeof(*ws));
    > + ws->name = name;
    > + }
    > +}
    > +EXPORT_SYMBOL_GPL(wakeup_source_prepare);
    > +
    > +/**
    > * wakeup_source_create - Create a struct wakeup_source object.
    > * @name: Name of the new wakeup source.
    > */
    > @@ -60,31 +77,41 @@ struct wakeup_source *wakeup_source_crea
    > {
    > struct wakeup_source *ws;
    >
    > - ws = kzalloc(sizeof(*ws), GFP_KERNEL);
    > + ws = kmalloc(sizeof(*ws), GFP_KERNEL);
    > if (!ws)
    > return NULL;
    >
    > - if (name)
    > - ws->name = kstrdup(name, GFP_KERNEL);
    > -
    > + wakeup_source_prepare(ws, name ? kstrdup(name, GFP_KERNEL) : NULL);
    > return ws;
    > }
    > EXPORT_SYMBOL_GPL(wakeup_source_create);
    >
    > /**
    > - * wakeup_source_destroy - Destroy a struct wakeup_source object.
    > - * @ws: Wakeup source to destroy.
    > + * wakeup_source_drop - Prepare a struct wakeup_source object for destruction.
    > + * @ws: Wakeup source to prepare for destruction.
    > *
    > * Callers must ensure that __pm_stay_awake() or __pm_wakeup_event() will never
    > * be run in parallel with this function for the same wakeup source object.
    > */
    > -void wakeup_source_destroy(struct wakeup_source *ws)
    > +void wakeup_source_drop(struct wakeup_source *ws)
    > {
    > if (!ws)
    > return;
    >
    > del_timer_sync(&ws->timer);
    > __pm_relax(ws);
    > +}
    > +EXPORT_SYMBOL_GPL(wakeup_source_drop);
    > +
    > +/**
    > + * wakeup_source_destroy - Destroy a struct wakeup_source object.
    > + * @ws: Wakeup source to destroy.
    > + *
    > + * Use only for wakeup source objects created with wakeup_source_create().
    > + */
    > +void wakeup_source_destroy(struct wakeup_source *ws)
    > +{
    > + wakeup_source_drop(ws);
    > kfree(ws->name);
    > kfree(ws);
    > }
    > Index: linux/include/linux/pm_wakeup.h
    > ===================================================================
    > --- linux.orig/include/linux/pm_wakeup.h
    > +++ linux/include/linux/pm_wakeup.h
    > @@ -73,7 +73,9 @@ static inline bool device_may_wakeup(str
    > }
    >
    > /* drivers/base/power/wakeup.c */
    > +extern void wakeup_source_prepare(struct wakeup_source *ws, const char *name);
    > extern struct wakeup_source *wakeup_source_create(const char *name);
    > +extern void wakeup_source_drop(struct wakeup_source *ws);
    > extern void wakeup_source_destroy(struct wakeup_source *ws);
    > extern void wakeup_source_add(struct wakeup_source *ws);
    > extern void wakeup_source_remove(struct wakeup_source *ws);
    > @@ -103,11 +105,16 @@ static inline bool device_can_wakeup(str
    > return dev->power.can_wakeup;
    > }
    >
    > +static inline void wakeup_source_prepare(struct wakeup_source *ws,
    > + const char *name) {}
    > +
    > static inline struct wakeup_source *wakeup_source_create(const char *name)
    > {
    > return NULL;
    > }
    >
    > +static inline void wakeup_source_drop(struct wakeup_source *ws) {}
    > +
    > static inline void wakeup_source_destroy(struct wakeup_source *ws) {}
    >
    > static inline void wakeup_source_add(struct wakeup_source *ws) {}
    > @@ -165,4 +172,17 @@ static inline void pm_wakeup_event(struc
    >
    > #endif /* !CONFIG_PM_SLEEP */
    >
    > +static inline void wakeup_source_init(struct wakeup_source *ws,
    > + const char *name)
    > +{
    > + wakeup_source_prepare(ws, name);
    > + wakeup_source_add(ws);
    > +}
    > +
    > +static inline void wakeup_source_trash(struct wakeup_source *ws)
    > +{
    > + wakeup_source_remove(ws);
    > + wakeup_source_drop(ws);
    > +}
    > +
    > #endif /* _LINUX_PM_WAKEUP_H */
    > --
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    >

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