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SubjectRe: [PATCH 1/4] lockdep: lock_set_subclass() fix
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On Mon, 2011-11-07 at 08:21 -0800, Tejun Heo wrote:

> > @@ -148,9 +148,9 @@ void clear_lock_stats(struct lock_class *class);
> > * This is embedded into specific lock instances:
> > */
> > struct lockdep_map {
> > + const char *name;
> > struct lock_class_key *key;
> > struct lock_class *class_cache[NR_LOCKDEP_CACHING_CLASSES];
> > - const char *name;
> > #ifdef CONFIG_LOCK_STAT
> > int cpu;
> > unsigned long ip;
>
> Probably fat comment explaining the ordering requirement here w/

yes.

> #define LOCKDEP_MAP_INIT_OFFSET offsetof(struct lockdep_map, class_cache)
>
> > diff --git a/kernel/lockdep.c b/kernel/lockdep.c
> > index e69434b..81855cf 100644
> > --- a/kernel/lockdep.c
> > +++ b/kernel/lockdep.c
> > @@ -2948,7 +2948,8 @@ static int mark_lock(struct task_struct *curr, struct held_lock *this,
> > void lockdep_init_map(struct lockdep_map *lock, const char *name,
> > struct lock_class_key *key, int subclass)
> > {
> > - memset(lock, 0, sizeof(*lock));
> > + kmemcheck_mark_initialized(lock, 2*sizeof(void *));
> > + memset(&lock->class_cache[0], 0, sizeof(*lock)-2*sizeof(void *));
>
> And something like the following?
>
> memset((void *)lock + LOCKDEP_MAP_INIT_OFFSET, 0,
> sizeof(*lock) - LOCKDEP_MAP_INIT_OFFSET);

Much better indeed!


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