From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH 11/18] fs: Introduce per-bucket inode hash locks Date: Mon, 18 Oct 2010 12:21:05 -0400 Message-ID: <20101018162105.GB9571@infradead.org> References: <1286515292-15882-1-git-send-email-david@fromorbit.com> <1286515292-15882-12-git-send-email-david@fromorbit.com> <20101008185409.GA29251@infradead.org> <20101016075703.GO19147@amd> <20101016161642.GC16861@infradead.org> <20101016171213.GC3240@amd> <20101017004610.GB29677@dastard> <20101017022539.GA3317@amd> <87iq0za32l.fsf@basil.nowhere.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Nick Piggin , Dave Chinner , Christoph Hellwig , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org To: Andi Kleen Return-path: Content-Disposition: inline In-Reply-To: <87iq0za32l.fsf@basil.nowhere.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org 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.