Re: [RFC][PATCH 0/8] PM: Implement autosleep and "wake locks"

["Rafael J. Wysocki" <rjw@sisk.pl>]

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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