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Merge branch 'core-debugobjects-for-linus' of git://git.kernel.org/pu…
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…b/scm/linux/kernel/git/tip/tip

* 'core-debugobjects-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timer: Use debugobjects to catch deletion of uninitialized timers
  timer: Setup uninitialized timer with a stub callback
  debugobjects: Extend to assert that an object is initialized
  debugobjects: Be smarter about static objects
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@torvalds
torvalds committed Jan 6, 2012
2 parents 07d106d + dc4218b commit 8c717b7
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Showing 4 changed files with 162 additions and 10 deletions.
50 changes: 50 additions & 0 deletions Documentation/DocBook/debugobjects.tmpl
View file
Expand Up @@ -96,6 +96,7 @@
<listitem><para>debug_object_deactivate</para></listitem>
<listitem><para>debug_object_destroy</para></listitem>
<listitem><para>debug_object_free</para></listitem>
<listitem><para>debug_object_assert_init</para></listitem>
</itemizedlist>
Each of these functions takes the address of the real object and
a pointer to the object type specific debug description
Expand Down Expand Up @@ -273,6 +274,26 @@
debug checks.
</para>
</sect1>

<sect1 id="debug_object_assert_init">
<title>debug_object_assert_init</title>
<para>
This function is called to assert that an object has been
initialized.
</para>
<para>
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.
</para>
<para>
When the real object is already tracked by debugobjects it is
ignored.
</para>
</sect1>
</chapter>
<chapter id="fixupfunctions">
<title>Fixup functions</title>
Expand Down Expand Up @@ -381,6 +402,35 @@
statistics.
</para>
</sect1>
<sect1 id="fixup_assert_init">
<title>fixup_assert_init</title>
<para>
This function is called from the debug code whenever a problem
in debug_object_assert_init is detected.
</para>
<para>
Called from debug_object_assert_init() with a hardcoded state
ODEBUG_STATE_NOTAVAILABLE when the object is not found in the
debug bucket.
</para>
<para>
The function returns 1 when the fixup was successful,
otherwise 0. The return value is used to update the
statistics.
</para>
<para>
Note, this function should make sure debug_object_init() is
called before returning.
</para>
<para>
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.
</para>
</sect1>
</chapter>
<chapter id="bugs">
<title>Known Bugs And Assumptions</title>
Expand Down
6 changes: 6 additions & 0 deletions include/linux/debugobjects.h
View file
Expand Up @@ -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;
Expand All @@ -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
Expand All @@ -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:
Expand All @@ -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) { }
Expand Down
62 changes: 56 additions & 6 deletions kernel/timer.c
View file
Expand Up @@ -427,6 +427,12 @@ static int timer_fixup_init(void *addr, enum debug_obj_state state)
}
}

/* Stub timer callback for improperly used timers. */
static void stub_timer(unsigned long data)
{
WARN_ON(1);
}

/*
* fixup_activate is called when:
* - an active object is activated
Expand All @@ -450,7 +456,8 @@ static int timer_fixup_activate(void *addr, enum debug_obj_state state)
debug_object_activate(timer, &timer_debug_descr);
return 0;
} else {
WARN_ON_ONCE(1);
setup_timer(timer, stub_timer, 0);
return 1;
}
return 0;

Expand Down Expand Up @@ -480,12 +487,40 @@ static int timer_fixup_free(void *addr, enum debug_obj_state state)
}
}

/*
* fixup_assert_init is called when:
* - an untracked/uninit-ed object is found
*/
static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
{
struct timer_list *timer = addr;

switch (state) {
case ODEBUG_STATE_NOTAVAILABLE:
if (timer->entry.prev == TIMER_ENTRY_STATIC) {
/*
* This is not really a fixup. The timer was
* statically initialized. We just make sure that it
* is tracked in the object tracker.
*/
debug_object_init(timer, &timer_debug_descr);
return 0;
} else {
setup_timer(timer, stub_timer, 0);
return 1;
}
default:
return 0;
}
}

static struct debug_obj_descr timer_debug_descr = {
.name = "timer_list",
.debug_hint = timer_debug_hint,
.fixup_init = timer_fixup_init,
.fixup_activate = timer_fixup_activate,
.fixup_free = timer_fixup_free,
.name = "timer_list",
.debug_hint = timer_debug_hint,
.fixup_init = timer_fixup_init,
.fixup_activate = timer_fixup_activate,
.fixup_free = timer_fixup_free,
.fixup_assert_init = timer_fixup_assert_init,
};

static inline void debug_timer_init(struct timer_list *timer)
Expand All @@ -508,6 +543,11 @@ static inline void debug_timer_free(struct timer_list *timer)
debug_object_free(timer, &timer_debug_descr);
}

static inline void debug_timer_assert_init(struct timer_list *timer)
{
debug_object_assert_init(timer, &timer_debug_descr);
}

static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key);
Expand All @@ -531,6 +571,7 @@ EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
static inline void debug_timer_init(struct timer_list *timer) { }
static inline void debug_timer_activate(struct timer_list *timer) { }
static inline void debug_timer_deactivate(struct timer_list *timer) { }
static inline void debug_timer_assert_init(struct timer_list *timer) { }
#endif

static inline void debug_init(struct timer_list *timer)
Expand All @@ -552,6 +593,11 @@ static inline void debug_deactivate(struct timer_list *timer)
trace_timer_cancel(timer);
}

static inline void debug_assert_init(struct timer_list *timer)
{
debug_timer_assert_init(timer);
}

static void __init_timer(struct timer_list *timer,
const char *name,
struct lock_class_key *key)
Expand Down Expand Up @@ -902,6 +948,8 @@ int del_timer(struct timer_list *timer)
unsigned long flags;
int ret = 0;

debug_assert_init(timer);

timer_stats_timer_clear_start_info(timer);
if (timer_pending(timer)) {
base = lock_timer_base(timer, &flags);
Expand Down Expand Up @@ -932,6 +980,8 @@ int try_to_del_timer_sync(struct timer_list *timer)
unsigned long flags;
int ret = -1;

debug_assert_init(timer);

base = lock_timer_base(timer, &flags);

if (base->running_timer == timer)
Expand Down
54 changes: 50 additions & 4 deletions lib/debugobjects.c
View file
Expand Up @@ -268,12 +268,16 @@ static void debug_print_object(struct debug_obj *obj, char *msg)
* Try to repair the damage, so we have a better chance to get useful
* debug output.
*/
static void
static int
debug_object_fixup(int (*fixup)(void *addr, enum debug_obj_state state),
void * addr, enum debug_obj_state state)
{
int fixed = 0;

if (fixup)
debug_objects_fixups += fixup(addr, state);
fixed = fixup(addr, state);
debug_objects_fixups += fixed;
return fixed;
}

static void debug_object_is_on_stack(void *addr, int onstack)
Expand Down Expand Up @@ -386,6 +390,9 @@ void debug_object_activate(void *addr, struct debug_obj_descr *descr)
struct debug_bucket *db;
struct debug_obj *obj;
unsigned long flags;
struct debug_obj o = { .object = addr,
.state = ODEBUG_STATE_NOTAVAILABLE,
.descr = descr };

if (!debug_objects_enabled)
return;
Expand Down Expand Up @@ -425,8 +432,9 @@ void debug_object_activate(void *addr, struct debug_obj_descr *descr)
* let the type specific code decide whether this is
* true or not.
*/
debug_object_fixup(descr->fixup_activate, addr,
ODEBUG_STATE_NOTAVAILABLE);
if (debug_object_fixup(descr->fixup_activate, addr,
ODEBUG_STATE_NOTAVAILABLE))
debug_print_object(&o, "activate");
}

/**
Expand Down Expand Up @@ -562,6 +570,44 @@ void debug_object_free(void *addr, struct debug_obj_descr *descr)
raw_spin_unlock_irqrestore(&db->lock, flags);
}

/**
* 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
Expand Down

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