Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753994AbZFAOVQ (ORCPT ); Mon, 1 Jun 2009 10:21:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751114AbZFAOVD (ORCPT ); Mon, 1 Jun 2009 10:21:03 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:45152 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751248AbZFAOVD (ORCPT ); Mon, 1 Jun 2009 10:21:03 -0400 Date: Mon, 1 Jun 2009 10:21:04 -0400 From: Christoph Hellwig To: Ingo Molnar Cc: linux-kernel@vger.kernel.org Subject: fishy code in arch/x86/kernel/tsc.c:time_cpufreq_notifier() Message-ID: <20090601142104.GA15907@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.18 (2008-05-17) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1057 Lines: 36 Just notice the following error from gcc 4.4: arch/x86/kernel/tsc.c: In function 'time_cpufreq_notifier': arch/x86/kernel/tsc.c:634: warning: 'dummy' may be used uninitialized in this function dummy is only used in the following way in this function: lpj = &dummy; and then dummy might be overriden in the following odd way: if (!(freq->flags & CPUFREQ_CONST_LOOPS)) #ifdef CONFIG_SMP lpj = &cpu_data(freq->cpu).loops_per_jiffy; #else lpj = &boot_cpu_data.loops_per_jiffy; #endif and then is used in if (!ref_freq) { ref_freq = freq->old; loops_per_jiffy_ref = *lpj; tsc_khz_ref = tsc_khz; } to me that looks like it can indeed be used unitialized for the case where we do have CONFIG_SMP set, freq->flags & CPUFREQ_CONST_LOOPS is true and ref_freq is false. Can that case actually happen? -- 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/