From mboxrd@z Thu Jan 1 00:00:00 1970 From: Peter Zijlstra Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Date: Wed, 13 Feb 2019 19:33:14 +0100 Message-ID: <20190213183314.GB32494@hirez.programming.kicks-ass.net> References: <20190211172948.3322-1-will.deacon@arm.com> <20190213172047.GH6346@brain-police> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: Sender: linux-kernel-owner@vger.kernel.org To: Linus Torvalds Cc: Will Deacon , linux-arch , Linux List Kernel Mailing , "Paul E. McKenney" , Benjamin Herrenschmidt , Arnd Bergmann , Andrea Parri , Daniel Lustig , David Howells , Alan Stern , Tony Luck List-Id: linux-arch.vger.kernel.org On Wed, Feb 13, 2019 at 10:27:09AM -0800, Linus Torvalds wrote: > Yeah, yeah, there's the SGI "SN" platform that apparently has a bug, > so because of that platform problem maybe it needs the more complex > "use a flag" model. But even the complex model isn't _hugely_ > complex. > > But we *could* first just do the mmiowb() unconditionally in the ia64 > unlocking code, and then see if anybody notices? > > Tony, comments? Are there any SGI SN machines around any more? I think the last time this came up, it was said that those people still running Linux on Itanium were running old disto kernels, not upstream. So yeah, we could probably do whatever and nobody would ever notice, except maybe Al, who is rumoured to still have an ia64 :-) From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:54218 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726940AbfBMSd3 (ORCPT ); Wed, 13 Feb 2019 13:33:29 -0500 Date: Wed, 13 Feb 2019 19:33:14 +0100 From: Peter Zijlstra Subject: Re: [RFC PATCH] docs/memory-barriers.txt: Rewrite "KERNEL I/O BARRIER EFFECTS" section Message-ID: <20190213183314.GB32494@hirez.programming.kicks-ass.net> References: <20190211172948.3322-1-will.deacon@arm.com> <20190213172047.GH6346@brain-police> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: linux-arch-owner@vger.kernel.org List-ID: To: Linus Torvalds Cc: Will Deacon , linux-arch , Linux List Kernel Mailing , "Paul E. McKenney" , Benjamin Herrenschmidt , Arnd Bergmann , Andrea Parri , Daniel Lustig , David Howells , Alan Stern , Tony Luck Message-ID: <20190213183314.urbDn-ScmgUTWNrogRTV3g2ZY0EJJo_GGdJFG4wyrxg@z> On Wed, Feb 13, 2019 at 10:27:09AM -0800, Linus Torvalds wrote: > Yeah, yeah, there's the SGI "SN" platform that apparently has a bug, > so because of that platform problem maybe it needs the more complex > "use a flag" model. But even the complex model isn't _hugely_ > complex. > > But we *could* first just do the mmiowb() unconditionally in the ia64 > unlocking code, and then see if anybody notices? > > Tony, comments? Are there any SGI SN machines around any more? I think the last time this came up, it was said that those people still running Linux on Itanium were running old disto kernels, not upstream. So yeah, we could probably do whatever and nobody would ever notice, except maybe Al, who is rumoured to still have an ia64 :-)