From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from biscayne-one-station.mit.edu (BISCAYNE-ONE-STATION.MIT.EDU [18.7.7.80]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id B61DEB7EDB for ; Fri, 16 Oct 2009 03:46:55 +1100 (EST) Date: Thu, 15 Oct 2009 12:46:13 -0400 (EDT) From: Tim Abbott To: Benjamin Herrenschmidt Subject: Re: powerpc problem with .data.page_aligned -> __page_aligned_data conversion In-Reply-To: <1255584772.2347.86.camel@pasglop> Message-ID: References: <1255584772.2347.86.camel@pasglop> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: linuxppc-dev@lists.ozlabs.org, Andrew Morton , Linus Torvalds , sam@ravnborg.org, "linux-kernel@vger.kernel.org" List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Thu, 15 Oct 2009, Benjamin Herrenschmidt wrote: > What do you recommend I do ? > I can ban gcc < 4.3 but that's a bit harsh :-) Yeah, let's try to avoid that. > I know a few people that won't be happy to be unable to build newer > kernels with current distro gccs. > > Or can do the above making the macro definition drop the alignment part > on powerpc. Will work for now, but will require great care to avoid > subtle and nasty breakage (basically same as before) Yeah, I'd be afraid that changing the generic __page_aligned_data might cause unexpected problems on some other architecture. > Or maybe I can do the above but only when using gcc < 4.3 so at least if > the breakage happen, that will only be with older gccs ... It sounds like from your grepping, you don't believe that dropping the alignment part will actually cause any problems on powerpc currently? If so, dropping the alignment part on powerpc with gcc < 4.3 seems best to me. It limits the workaround in time (eventually gcc < 4.3 will be history). It also limits it in scope (to powerpc), where at least you're well aware of the issue and can pay attention to new code being added that uses __page_aligned_data. Since most code that has page-aligned data structures is architecture-specific, there's a good chance that any new code that would break will be at least looked at by you (and given how few places it is used currently, this seems pretty unlikely to actually come up). -Tim Abbott