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Date: Tue, 16 Mar 2010 15:54:02 +0900 From: Tejun Heo <tj@...nel.org> To: Ingo Molnar <mingo@...e.hu> CC: Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, lkml <linux-kernel@...r.kernel.org>, Lee Schermerhorn <Lee.Schermerhorn@...com>, Christoph Lameter <cl@...ux-foundation.org> Subject: Re: [RFC] remove implicit slab.h inclusion from percpu.h Hello, Ingo. On 03/16/2010 03:17 PM, Ingo Molnar wrote: > ( /me mumbles something about not having a patch in the email to review and > pulling the tree. 200k patch is just fine for lkml - i've attached it below > for easier review. percpu.h and percpu.c has the meat of the changes. ) I wanted to keep the discussion high level while giving a general idea about the extent of necessary changes. I'll include the patch from now on. > i like the dependency reduction. Noticed one small detail: > > this new 2000-lines #ifdef block percpu.c: > > +#ifdef CONFIG_SMP > +#else /* CONFIG_SMP */ > +#endif /* CONFIG_SMP */ > > feels a bit lame. A separate percpu_up.c file would be nicer i suppose? Sure. > Also, why should we make this opt-in and expose a wide range of configs to > build breakages? A more gradual approach would be to write a simple script > that adds a slab.h include to all .c's that include percpu.h, directly or > indirectly. > > You can map the pattern experimentally: the insertion pattern could be built > from the x86 allmodconfig build you did [i.e. extend the pattern until you > make it build on allmodconfig] - that would cover most cases in practice (not > just allmodconfig) - and would cover most architectures as well. I don't really get the 'experimental' part but if I count all the files which ends up including percpu.h directly or indirectly on allmodconfig it ends up including much more .c files than necessasry - 11203 to be exact, ~20 times more than necessary. Inclusions from .c files definitely are much less troublesome so the situation would be better than now but we'll still end up with a LOT of bogus inclusions without any good way to eventually remove them. Maybe a better way is to grab for slab API usages in .c files which don't have slab.h inclusion. If breaking the dependency is the way to go, I can definitely write up some scripts and do test builds on some archs. There sure will be some fallouts but I think it won't be too bad. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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