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Date: Tue, 28 Apr 2009 08:15:57 +0200 From: Nick Piggin <npiggin@...e.de> To: Valdis.Kletnieks@...edu Cc: Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, mm-commits@...r.kernel.org Subject: Re: mmotm 2009-04-24-18-14 uploaded - NVidia indigestion On Mon, Apr 27, 2009 at 02:45:15PM -0400, Valdis.Kletnieks@...edu wrote: > On Sat, 25 Apr 2009 07:24:34 +0200, Nick Piggin said: > > > > #include <linux/version.h> > > > #include <linux/utsname.h> > > > int main() { > > > if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,0)) { > > > return 0; > > > } else { > > > return 1; > > > } > > > Yeah BUILD_BUG_ON does work like that. I can't for the life of me > > understand why it triggered though. Is anything in your external > > code calling kmalloc_slab directly? > > See above - I didn't think LINUX_VERSION_CODE cared about kmalloc, but > I could be wrong on this. ;) > > > What's the preprocessor output look like? > > The problem appears to be that if you only include version.h and utsname.h, > and *don't* actually reference kmalloc_slab, it doesn't know that the size_t > is actually a constant, so it whinges. Most modules end up doing at least > one kmalloc(), so kmalloc() and kmalloc_slab() get inlined, the constant 'size' > gets propogated, and life is good. If you *don't* call kmalloc(), bad things > happen. ;) Hmm, yes if you build without -O, then it appears like the compiler trips over this. I wouldn't be unhappy with just removing the BUILD_BUG_ON, but shouldn't the module be using -O[s2]? -- 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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