From a5d8e467f83f6672104f276223a88e3b50cbd375 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Sat, 17 Apr 2010 08:48:38 -0400 Subject: Debugobjects transition check Implement a basic state machine checker in the debugobjects. This state machine checker detects races and inconsistencies within the "active" life of a debugobject. The checker only keeps track of the current state; all the state machine logic is kept at the object instance level. The checker works by adding a supplementary "unsigned int astate" field to the debug_obj structure. It keeps track of the current "active state" of the object. The only constraints that are imposed on the states by the debugobjects system is that: - activation of an object sets the current active state to 0, - deactivation of an object expects the current active state to be 0. For the rest of the states, the state mapping is determined by the specific object instance. Therefore, the logic keeping track of the state machine is within the specialized instance, without any need to know about it at the debugobject level. The current object active state is changed by calling: debug_object_active_state(addr, descr, expect, next) where "expect" is the expected state and "next" is the next state to move to if the expected state is found. A warning is generated if the expected is not found. Signed-off-by: Mathieu Desnoyers Reviewed-by: Thomas Gleixner Acked-by: David S. Miller CC: "Paul E. McKenney" CC: akpm@linux-foundation.org CC: mingo@elte.hu CC: laijs@cn.fujitsu.com CC: dipankar@in.ibm.com CC: josh@joshtriplett.org CC: dvhltc@us.ibm.com CC: niv@us.ibm.com CC: peterz@infradead.org CC: rostedt@goodmis.org CC: Valdis.Kletnieks@vt.edu CC: dhowells@redhat.com CC: eric.dumazet@gmail.com CC: Alexey Dobriyan Signed-off-by: Paul E. McKenney diff --git a/include/linux/debugobjects.h b/include/linux/debugobjects.h index 8c243aa..597692f 100644 --- a/include/linux/debugobjects.h +++ b/include/linux/debugobjects.h @@ -20,12 +20,14 @@ struct debug_obj_descr; * struct debug_obj - representaion of an tracked object * @node: hlist node to link the object into the tracker list * @state: tracked object state + * @astate: current active state * @object: pointer to the real object * @descr: pointer to an object type specific debug description structure */ struct debug_obj { struct hlist_node node; enum debug_obj_state state; + unsigned int astate; void *object; struct debug_obj_descr *descr; }; @@ -60,6 +62,15 @@ 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); +/* + * Active state: + * - Set at 0 upon initialization. + * - Must return to 0 before deactivation. + */ +extern void +debug_object_active_state(void *addr, struct debug_obj_descr *descr, + unsigned int expect, unsigned int next); + extern void debug_objects_early_init(void); extern void debug_objects_mem_init(void); #else diff --git a/lib/debugobjects.c b/lib/debugobjects.c index b862b30..076464f 100644 --- a/lib/debugobjects.c +++ b/lib/debugobjects.c @@ -141,6 +141,7 @@ alloc_object(void *addr, struct debug_bucket *b, struct debug_obj_descr *descr) obj->object = addr; obj->descr = descr; obj->state = ODEBUG_STATE_NONE; + obj->astate = 0; hlist_del(&obj->node); hlist_add_head(&obj->node, &b->list); @@ -252,8 +253,10 @@ static void debug_print_object(struct debug_obj *obj, char *msg) if (limit < 5 && obj->descr != descr_test) { limit++; - WARN(1, KERN_ERR "ODEBUG: %s %s object type: %s\n", msg, - obj_states[obj->state], obj->descr->name); + WARN(1, KERN_ERR "ODEBUG: %s %s (active state %u) " + "object type: %s\n", + msg, obj_states[obj->state], obj->astate, + obj->descr->name); } debug_objects_warnings++; } @@ -447,7 +450,10 @@ void debug_object_deactivate(void *addr, struct debug_obj_descr *descr) case ODEBUG_STATE_INIT: case ODEBUG_STATE_INACTIVE: case ODEBUG_STATE_ACTIVE: - obj->state = ODEBUG_STATE_INACTIVE; + if (!obj->astate) + obj->state = ODEBUG_STATE_INACTIVE; + else + debug_print_object(obj, "deactivate"); break; case ODEBUG_STATE_DESTROYED: @@ -553,6 +559,53 @@ out_unlock: 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 + * @expect: expected state + * @next: state to move to if expected state is found + */ +void +debug_object_active_state(void *addr, struct debug_obj_descr *descr, + unsigned int expect, unsigned int next) +{ + 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) { + switch (obj->state) { + case ODEBUG_STATE_ACTIVE: + if (obj->astate == expect) + obj->astate = next; + else + debug_print_object(obj, "active_state"); + break; + + default: + debug_print_object(obj, "active_state"); + break; + } + } else { + struct debug_obj o = { .object = addr, + .state = ODEBUG_STATE_NOTAVAILABLE, + .descr = descr }; + + debug_print_object(&o, "active_state"); + } + + raw_spin_unlock_irqrestore(&db->lock, flags); +} + #ifdef CONFIG_DEBUG_OBJECTS_FREE static void __debug_check_no_obj_freed(const void *address, unsigned long size) { -- cgit v0.10.2