From mboxrd@z Thu Jan 1 00:00:00 1970 From: Greg Kroah-Hartman Subject: Re: [PATCH 21/26] tty: Convert tty_struct bitfield to bools Date: Wed, 3 Sep 2014 10:56:06 -0700 Message-ID: <20140903175606.GA9740@kroah.com> References: <1409693975-1028-1-git-send-email-peter@hurleysoftware.com> <1409693975-1028-22-git-send-email-peter@hurleysoftware.com> <20140903115852.5a720754@alan.etchedpixels.co.uk> <54070643.9080903@hurleysoftware.com> <20140903131919.0d970b6f@alan.etchedpixels.co.uk> <54072F75.70107@hurleysoftware.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <54072F75.70107@hurleysoftware.com> Sender: linux-kernel-owner@vger.kernel.org To: Peter Hurley Cc: One Thousand Gnomes , Jiri Slaby , linux-serial@vger.kernel.org, linux-kernel@vger.kernel.org List-Id: linux-serial@vger.kernel.org On Wed, Sep 03, 2014 at 11:10:45AM -0400, Peter Hurley wrote: > On 09/03/2014 08:19 AM, One Thousand Gnomes wrote: > >> Ahh. Thanks for the insight, Alan. > >> > >> But set_bit() et. al. will generate an incredible amount of churn; > >> what if I split the fields up to prevent false-sharing? > > > > Do you feel lucky ;-) > > Hahaha :) > > > I'd rather set_bit and friends were used. They exist largely for this > > kind of reason and they also have atomic test/set methods which may in > > the longer term be very useful. > > > > Yes it is churn can't argue with that. > > Yuck. There should be a better way. IXANY mode is suddenly going to > have a ton of unnecessary bus locks on x86. True, but at least it will be correct, which I'm guessing today it isn't :( > Note the ctrl_status field is a byte as well, which can't be RMW'ed by > the bit-locked primitives, and definitely should not be aggregated with > any adjacent field. Never trust what an ia64 compiler can, and will, do... greg k-h