From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 1E81E1591F1; Tue, 9 Jul 2024 14:23:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720535003; cv=none; b=JX3ei341pqwIroGpdYkNpQg4AFzzwBRVjtgwTiacR3CD8XMLhMPH51Wi99Mk3h+048Elpd+aLU4HOympMDeDJjVWHJ0sQS56LeYw/G33QIQgmsn3T+DVXO16DWGYu9qYgPWPBiiSFiDNHTd2tu5xoR0leoJ9XivqUjOyus+MH90= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1720535003; c=relaxed/simple; bh=eXgJ4wYdqysY/qkd6HNpgdu1snkkrsiOyckPHx7KNYo=; h=Message-ID:Subject:From:To:Cc:Date:In-Reply-To:References: Content-Type:MIME-Version; b=WjHn9aVUg+FUyetGJsJaV6Z564SZmBSItGNlDv38nFK3r0S7/wrX2AbctuyNPt4d0Rq8ALlc84F4u1cU61nuxMt4qOg3tzRIW0m17trJGbp+336OPJKjqnNqkOeE0l2HCGFp8zPQyq0mxTYs0/QML7l60lLY+EdvfWreT0Pe7NA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=d2ry0i/l; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="d2ry0i/l" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 6AACDC4AF0A; Tue, 9 Jul 2024 14:23:22 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1720535002; bh=eXgJ4wYdqysY/qkd6HNpgdu1snkkrsiOyckPHx7KNYo=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=d2ry0i/l8a/eH2+9Te6S1AqQwFentP4VCejtrS86kNwcFtlXGjO7nxQpUEMDW3j/F 2cdgFoPxLj59UVDNJwoE+hYz3QDQoIQCpOGYhHosnP3j9EZLFoOg1En1TSPHR8q+5G UjHYPC7P/cT24GfMJhJKyC8xPzwXRBwRCgCTyQUCY5+EzJIUu66Bob60NIRhsZMG8i tiBIgYlkQt2+JzFgoKrgadgclkTS2wN2gg98NPdmKqoo3qxhvZ+nI3DP6gfR3TUc9f 9VnaDFXirCQOnF/U8mHzL+cBKXJu27MiPWwn4TH51v4a+r1C3zYFbxrd3S0MIC1wID umt4z5W2gVRzw== Message-ID: <6ab599393503a50b4b708767f320a46388aa95f2.camel@kernel.org> Subject: Re: [jlayton:mgtime 5/13] inode.c:undefined reference to `__invalid_cmpxchg_size' From: Jeff Layton To: Arnd Bergmann , Geert Uytterhoeven Cc: linux-m68k@lists.linux-m68k.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org Date: Tue, 09 Jul 2024 10:23:21 -0400 In-Reply-To: References: <202407091931.mztaeJHw-lkp@intel.com> Autocrypt: addr=jlayton@kernel.org; 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charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.4 (3.50.4-1.fc39) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 On Tue, 2024-07-09 at 16:16 +0200, Arnd Bergmann wrote: > On Tue, Jul 9, 2024, at 15:45, Geert Uytterhoeven wrote: > > On Tue, Jul 9, 2024 at 1:58=E2=80=AFPM Jeff Layton > > wrote: > > > I've been getting some of these warning emails from the KTR. I > > > think > > > this is in reference to this patch, which adds a 64-bit > > > try_cmpxchg in > > > the timestamp handling code: > > >=20 > > > =C2=A0=C2=A0=C2=A0 > > > https://lore.kernel.org/linux-fsdevel/20240708-mgtime-v4-0-a0f3c6fb57= f3@kernel.org/ > > >=20 > > > On m68k, there is a prototype for __invalid_cmpxchg_size, but no > > > actual > > > function, AFAICT. Should that be defined somewhere, or is this a > > > deliberate way to force a build break in this case? > >=20 > > It's a deliberate way to break the build. > >=20 > > > More to the point though: do I need to do anything special for > > > m86k > > > here (or for other arches that can't do a native 64-bit cmpxchg)? > >=20 > > 64-bit cmpxchg() is only guaranteed to exist on 64-bit platforms. > > See also > > https://elixir.bootlin.com/linux/latest/source/include/asm-generic/cmpx= chg.h#L62 > >=20 > > I think you can use arch_cmpxchg64(), though. >=20 > arch_cmpxchg64() is an internal helper provided by some > architectures. Driver code should use cmpxchg64() for > the explicitly 64-bit sized atomic operation. >=20 > I'm fairly sure we still don't provide this across all > 32-bit architectures though: on architectures that have > 64-bit atomics (i686, armv6k, ...) these can be provided > architecture specific code, and on non-SMP kernels they > can use the generic fallback through > generic_cmpxchg64_local(), but on SMP architectures without > native atomics you need a Kconfig dependency to turn off > the particular code. >=20 I think the simplest solution is to make the floor value I'm tracking be an atomic64_t. That looks like it should smooth over the differences between arches. I'm testing a patch to do that now. Thanks! --=20 Jeff Layton