Re: [PATCH 11/18] fs: Introduce per-bucket inode hash locks

Christoph Hellwig
2010-10-18T16:21:19Z

On Mon, Oct 18, 2010 at 06:16:50PM +0200, Andi Kleen wrote:
> > Hiding the type of lock, and hiding the fact that it sets the low bit?
> > I don't agree. We don't have synchronization in our data structures,
> > where possible, because it is just restrictive or goes wrong when people
> > don't think enough about the locking.
>
> I fully agree. The old skb lists in networking made this mistake
> long ago and it was a big problem, until people essentially stopped
> using it (always using __ variants) and it was eventually removed.
>
> Magic locking in data structures is usually a bad idea.

Err, there is no implicit locking in the calls to hlist_*. There
is just two small wrappers for the bit-lock/unlock so that the callers
don't have to know how the lock is overloaded onto the pointer in the
list head.