Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id ; Mon, 9 Sep 2002 04:13:13 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id ; Mon, 9 Sep 2002 04:13:13 -0400 Received: from dp.samba.org ([66.70.73.150]:15024 "EHLO lists.samba.org") by vger.kernel.org with ESMTP id ; Mon, 9 Sep 2002 04:13:10 -0400 From: Rusty Russell To: "David S. Miller" Cc: pavel@suse.cz, torvalds@transmeta.com, linux-kernel@vger.kernel.org, akpm@zip.com.au Subject: Re: [PATCH] Important per-cpu fix. In-reply-to: Your message of "Sun, 08 Sep 2002 23:13:04 MST." <20020908.231304.30400540.davem@redhat.com> Date: Mon, 09 Sep 2002 18:17:22 +1000 Message-Id: <20020909081754.EC8382C09D@lists.samba.org> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2773 Lines: 60 In message <20020908.231304.30400540.davem@redhat.com> you write: > From: Rusty Russell > Date: Mon, 09 Sep 2002 13:45:02 +1000 > > /* FIXME: Initializer required so gcc 2.96 doesn't put in BSS */ > DEFINE_PER_CPU(int, xxx) = 0; > > everywhere, which can be deleted later > > Why everywhere? If you do it in the macro, then when you want > to delete the initializer remove the macro arg. Then you cover > both in-kernel and cases in external sources because the build > will break for them so they'll know to fixup their macro invocation. So, you break everyone's compile later *and* you have to figure out which initializers were required, and which ones were bogus. *Planning* to break an interface is just stupid. > See spinlock_t's declaration for older GCC versions, that is how we > traditionally deal with compiler bugs like this, explicitly so that it > is impossible to "miss" something and get it wrong. Yeah, but you can still leave a spinlock uninitialized, and it'll work. I'm not making an interface harder to use because of one of 17 architectures refuses to fix a bug in their toolchain. Just not happening, sorry. I want *you* to feel the pain, not spread it around by leaving turds throughout the code long after the bug is forgotten: diff -urpN --exclude TAGS -X /home/rusty/devel/kernel/kernel-patches/current-dontdiff --minimal working-2.5.33-cset-1.621/Makefile working-2.5.33-cset-1.621-catch-percpu/Makefile --- working-2.5.33-cset-1.621/Makefile 2002-09-09 13:31:44.000000000 +1000 +++ working-2.5.33-cset-1.621-catch-percpu/Makefile 2002-09-09 18:06:51.000000000 +1000 @@ -282,6 +282,8 @@ cmd_link_vmlinux = $(LD) $(LDFLAGS) $(LD -o vmlinux # set -e makes the rule exit immediately on error +# Final awk script makes sure per-cpu vars are in per-cpu section, as +# old gcc (eg egcs 2.92.11) ignores section attribute if uninitialized. define rule_link_vmlinux set -e @@ -292,6 +294,7 @@ define rule_link_vmlinux $(call cmd,link_vmlinux) echo 'cmd_$@ := $(cmd_link_vmlinux)' > $(@D)/.$(@F).cmd $(NM) vmlinux | grep -v '$compiled$\|$\.o$$$\|$ [aUw] $\|$\.\.ng$$$\|$LASH[RL]DI$' | sort > System.map + awk '/ __per_cpu_start$/ { IN_PER_CPU=1 } / __per_cpu_end$/ { IN_PER_CPU=0 } /__per_cpu$/ { if (!IN_PER_CPU) { print $3 " not in per-cpu section" > "/dev/stderr"; FOUND=1; } } END { exit FOUND; }' < System.map endef vmlinux: $(vmlinux-objs) FORCE -- Anyone who quotes me in their sig is an idiot. -- Rusty Russell. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/