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    SubjectRe: [PATCH 1/4] lockdep: lock_set_subclass() fix
    On Tue, Nov 08, 2011 at 08:56:55AM +0100, Peter Zijlstra wrote:
    > On Tue, 2011-11-08 at 10:58 +0800, Yong Zhang wrote:
    > > > 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;
    > > > 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 *));
    > >
    > > That means ->key have chance to be 0 at some time, right?
    >
    > How? We only memset from class_cache onwards, leaving name and key
    > untouched.

    Hmm, we don't touch key in your patch. My eyes was keeping on ->name.
    Sorry.

    But how do we deal with ->class_cache? Always set it in
    loop_up_lock_class()?

    Thanks,
    Yong


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