Re: [patch 01/52] kernel: add bl_list

Nick Piggin
2010-06-29T06:30:30Z

On Mon, Jun 28, 2010 at 02:37:39PM -0700, Paul E. McKenney wrote:
> On Thu, Jun 24, 2010 at 01:02:13PM +1000, npiggin@suse.de wrote:
> > Introduce a type of hlist that can support the use of the lowest bit in the
> > hlist_head. This will be subsequently used to implement per-bucket bit spinlock
> > for inode and dentry hashes.
> >
> > Signed-off-by: Nick Piggin <npiggin@suse.de>
>
> Looks good! One question on non-RCU pointer poisoning and a typo.
> When these are addressed (perhaps by showing me the error of my ways):
>
> Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
>

..

> > +static inline void hlist_bl_del(struct hlist_bl_node *n)
> > +{
> > + __hlist_bl_del(n);
> > + n->pprev = LIST_POISON2;
>
> OK, I'll bite... Why don't we poison the ->next pointer?

Ah, I took the code from list_nulls.h, but actually, except for the
hlist anchoring, the code is much more similar to the standard hlist.
This can be poisoned, and I'll go through and look for other possible
differences with hlists.

> > +/**
> > + * hlist_bl_del_init_rcu - deletes entry from hash list with re-initialization
> > + * @n: the element to delete from the hash list.
> > + *
> > + * Note: hlist_bl_unhashed() on the node return true after this. It is
> returns

Yes, thanks!