Commit b84d435c authored by Christine Chan's avatar Christine Chan Committed by Thomas Gleixner
Browse files

debugobjects: Extend to assert that an object is initialized 



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().

[ sboyd@codeaurora.org: Clarify commit message ]

Signed-off-by: default avatarChristine Chan <cschan@codeaurora.org>
Signed-off-by: default avatarStephen Boyd <sboyd@codeaurora.org>
Cc: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1320724108-20788-3-git-send-email-sboyd@codeaurora.org


Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
parent feac18dd

Documentation/DocBook/debugobjects.tmpl

+50 −0
Original line number Diff line number Diff line
@@ -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
@@ -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>
@@ -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>

include/linux/debugobjects.h

+6 −0
Original line number Diff line number Diff line
@@ -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) { }

lib/debugobjects.c

+38 −0
Original line number Diff line number Diff line
@@ -570,6 +570,44 @@ out_unlock: 
	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

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