[PATCHv2 2/3] debugobjects: Extend to assert that an object is initialized

Stephen Boyd
2011-11-08T03:49:05Z

From: Christine Chan <cschan@codeaurora.org>

Calling del_timer_sync() on an uninitialized timer leads to a
never ending loop in lock_timer_base() that spins checking for a
non-NULL timer base. Add an assertion to debugobjects to catch
usage of uninitialized objects so that we can initialize timers
in the del_timer_sync() path before it calls lock_timer_base().

Signed-off-by: Christine Chan <cschan@codeaurora.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
[sboyd: Clarify commit message]
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
---
Documentation/DocBook/debugobjects.tmpl | 50 +++++++++++++++++++++++++++++++
include/linux/debugobjects.h | 6 ++++
lib/debugobjects.c | 38 +++++++++++++++++++++++
3 files changed, 94 insertions(+), 0 deletions(-)

diff --git a/Documentation/DocBook/debugobjects.tmpl b/Documentation/DocBook/debugobjects.tmpl
index 08ff908..24979f6 100644
--- a/Documentation/DocBook/debugobjects.tmpl
+++ b/Documentation/DocBook/debugobjects.tmpl
@@ -96,6 +96,7 @@
debug_object_deactivate
debug_object_destroy
debug_object_free
+ debug_object_assert_init

Each of these functions takes the address of the real object and
a pointer to the object type specific debug description
@@ -273,6 +274,26 @@
debug checks.

</sect1>
+
+ <sect1 id="debug_object_assert_init">
+ debug_object_assert_init
+
+ This function is called to assert that an object has been
+ initialized.
+
+
+ When the real object is not tracked by debugobjects, it calls
+ fixup_assert_init of the object type description structure
+ provided by the caller, with the hardcoded object state
+ ODEBUG_NOT_AVAILABLE. The fixup function can correct the problem
+ by calling debug_object_init and other specific initializing
+ functions.
+
+
+ When the real object is already tracked by debugobjects it is
+ ignored.
+
+ </sect1>
</chapter>
<chapter id="fixupfunctions">
Fixup functions
@@ -381,6 +402,35 @@
statistics.

</sect1>
+ <sect1 id="fixup_assert_init">
+ fixup_assert_init
+
+ This function is called from the debug code whenever a problem
+ in debug_object_assert_init is detected.
+
+
+ Called from debug_object_assert_init() with a hardcoded state
+ ODEBUG_STATE_NOTAVAILABLE when the object is not found in the
+ debug bucket.
+
+
+ The function returns 1 when the fixup was successful,
+ otherwise 0. The return value is used to update the
+ statistics.
+
+
+ Note, this function should make sure debug_object_init() is
+ called before returning.
+
+
+ The handling of statically initialized objects is a special
+ case. The fixup function should check if this is a legitimate
+ case of a statically initialized object or not. In this case only
+ debug_object_init() should be called to make the object known to
+ the tracker. Then the function should return 0 because this is not
+ a real fixup.
+
+ </sect1>
</chapter>
<chapter id="bugs">
Known Bugs And Assumptions
diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h
index 65970b8..0e5f578 100644
--- a/include/linux/debugobjects.h
+++ b/include/linux/debugobjects.h
@@ -46,6 +46,8 @@ struct debug_obj {
* fails
* @fixup_free: fixup function, which is called when the free check
* fails
+ * @fixup_assert_init: fixup function, which is called when the assert_init
+ * check fails
*/
struct debug_obj_descr {
const char *name;
@@ -54,6 +56,7 @@ struct debug_obj_descr {
int (*fixup_activate) (void *addr, enum debug_obj_state state);
int (*fixup_destroy) (void *addr, enum debug_obj_state state);
int (*fixup_free) (void *addr, enum debug_obj_state state);
+ int (*fixup_assert_init)(void *addr, enum debug_obj_state state);
};

#ifdef CONFIG_DEBUG_OBJECTS
@@ -64,6 +67,7 @@ extern void debug_object_activate (void *addr, struct debug_obj_descr *descr);
extern void debug_object_deactivate(void *addr, struct debug_obj_descr *descr);
extern void debug_object_destroy (void *addr, struct debug_obj_descr *descr);
extern void debug_object_free (void *addr, struct debug_obj_descr *descr);
+extern void debug_object_assert_init(void *addr, struct debug_obj_descr *descr);

/*
* Active state:
@@ -89,6 +93,8 @@ static inline void
debug_object_destroy (void *addr, struct debug_obj_descr *descr) { }
static inline void
debug_object_free (void *addr, struct debug_obj_descr *descr) { }
+static inline void
+debug_object_assert_init(void *addr, struct debug_obj_descr *descr) { }

static inline void debug_objects_early_init(void) { }
static inline void debug_objects_mem_init(void) { }
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 0b07cc5..be066fa 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -570,6 +570,44 @@ out_unlock:
}

/**
+ * debug_object_assert_init - debug checks when object should be init-ed
+ * @addr: address of the object
+ * @descr: pointer to an object specific debug description structure
+ */
+void debug_object_assert_init(void *addr, struct debug_obj_descr *descr)
+{
+ struct debug_bucket *db;
+ struct debug_obj *obj;
+ unsigned long flags;
+
+ if (!debug_objects_enabled)
+ return;
+
+ db = get_bucket((unsigned long) addr);
+
+ raw_spin_lock_irqsave(&db->lock, flags);
+
+ obj = lookup_object(addr, db);
+ if (!obj) {
+ struct debug_obj o = { .object = addr,
+ .state = ODEBUG_STATE_NOTAVAILABLE,
+ .descr = descr };
+
+ raw_spin_unlock_irqrestore(&db->lock, flags);
+ /*
+ * Maybe the object is static. Let the type specific
+ * code decide what to do.
+ */
+ if (debug_object_fixup(descr->fixup_assert_init, addr,
+ ODEBUG_STATE_NOTAVAILABLE))
+ debug_print_object(&o, "assert_init");
+ return;
+ }
+
+ raw_spin_unlock_irqrestore(&db->lock, flags);
+}
+
+/**
* debug_object_active_state - debug checks object usage state machine
* @addr: address of the object
* @descr: pointer to an object specific debug description structure