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

[Rafael J. Wysocki]

On Wednesday, February 15, 2012, Arve Hjønnevåg wrote:
> 2012/2/14 Rafael J. Wysocki <rjw@xxxxxxx>:
> > On Tuesday, February 14, 2012, Arve Hjønnevåg wrote:
> >> On Mon, Feb 6, 2012 at 5:00 PM, Rafael J. Wysocki <rjw@xxxxxxx> 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.

Thanks,
Rafael


Signed-off-by: Rafael J. Wysocki <rjw@xxxxxxx>
---
 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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