Re: [PATCH v5 01/13] lockdep: Refactor lookup_chain_cache()

Byungchul Park
2017-01-19T10:07:25Z

On Thu, Jan 19, 2017 at 05:16:27PM +0800, Boqun Feng wrote:
> On Wed, Jan 18, 2017 at 10:17:27PM +0900, Byungchul Park wrote:
> > Currently, lookup_chain_cache() provides both 'lookup' and 'add'
> > functionalities in a function. However, each is useful. So this
> > patch makes lookup_chain_cache() only do 'lookup' functionality and
> > makes add_chain_cahce() only do 'add' functionality. And it's more
> > readable than before.
> >
> > Signed-off-by: Byungchul Park <byungchul.park@lge.com>
> > ---
> > kernel/locking/lockdep.c | 129 +++++++++++++++++++++++++++++------------------
> > 1 file changed, 81 insertions(+), 48 deletions(-)
> >
> > diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
> > index 4d7ffc0..f37156f 100644
> > --- a/kernel/locking/lockdep.c
> > +++ b/kernel/locking/lockdep.c
> > @@ -2109,15 +2109,9 @@ static int check_no_collision(struct task_struct *curr,
> > return 1;
> > }
> >
> > -/*
> > - * Look up a dependency chain. If the key is not present yet then
> > - * add it and return 1 - in this case the new dependency chain is
> > - * validated. If the key is already hashed, return 0.
> > - * (On return with 1 graph_lock is held.)
> > - */
>
> I think you'd better put some comments here for the behavior of
> add_chain_cache(), something like:
>
> /*
> * Add a dependency chain into chain hashtable.
> *
> * Must be called with graph_lock held.
> * Return 0 if fail to add the chain, and graph_lock is released.
> * Return 1 with graph_lock held if succeed.
> */

Yes. I will apply what you recommand.

Thank you very much. :)

Thanks,
Byungchul

>
> Regards,
> Boqun
>
> > -static inline int lookup_chain_cache(struct task_struct *curr,
> > - struct held_lock *hlock,
> > - u64 chain_key)
> > +static inline int add_chain_cache(struct task_struct *curr,
> > + struct held_lock *hlock,
> > + u64 chain_key)
> > {
> > struct lock_class *class = hlock_class(hlock);
> > struct hlist_head *hash_head = chainhashentry(chain_key);
> > @@ -2125,49 +2119,18 @@ static inline int lookup_chain_cache(struct task_struct *curr,
> > int i, j;
> >
> > /*
> > + * Allocate a new chain entry from the static array, and add
> > + * it to the hash:
> > + */
> > +
> > + /*
> > * We might need to take the graph lock, ensure we've got IRQs
> > * disabled to make this an IRQ-safe lock.. for recursion reasons
> > * lockdep won't complain about its own locking errors.
> > */
> > if (DEBUG_LOCKS_WARN_ON(!irqs_disabled()))
> > return 0;
> …