From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753980AbZETGV0 (ORCPT ); Wed, 20 May 2009 02:21:26 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752729AbZETGVT (ORCPT ); Wed, 20 May 2009 02:21:19 -0400 Received: from e38.co.us.ibm.com ([32.97.110.159]:44346 "EHLO e38.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752615AbZETGVS (ORCPT ); Wed, 20 May 2009 02:21:18 -0400 From: Subrata Modak To: Cc: Sachin P Sant , "H. Peter Anvin" , Frans Pop , Andi Kleen , Thomas Gleixner , Linux Kernel , Ingo Molnar , Subrata Modak , Balbir Singh Date: Wed, 20 May 2009 11:51:15 +0530 Message-Id: <20090520062115.23889.45487.sendpatchset@subratamodak.linux.ibm.com> Subject: [PATCH][Resend] Remove indirect variable usage at arch/x86/kernel/tsc.c Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, The following warning is generated on compilation: CC arch/x86/kernel/tsc.o 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 However, there seems to be no practical usage of variable 'dummy' in the following piece of code: 630 static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, 631 void *data) 632 { 633 struct cpufreq_freqs *freq = data; 634 unsigned long *lpj, dummy; 635 636 if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC)) 637 return 0; 638 639 lpj = &dummy; 640 if (!(freq->flags & CPUFREQ_CONST_LOOPS)) 641 #ifdef CONFIG_SMP 642 lpj = &cpu_data(freq->cpu).loops_per_jiffy; 643 #else 644 lpj = &boot_cpu_data.loops_per_jiffy; 645 #endif 646 'lpj' probably will get to point to some address after this if() statement. 647 if (!ref_freq) { 648 ref_freq = freq->old; 649 loops_per_jiffy_ref = *lpj; And, if it does, then "loops_per_jiffy_ref" will have a proper value, else, even with "lpj = &dummy" will not gurantee "loops_per_jiffy_ref = *lpj" to have the expected value. 650 tsc_khz_ref = tsc_khz; 651 } 652 if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || 653 (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || 654 (val == CPUFREQ_RESUMECHANGE)) { 655 *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); 656 657 tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); 658 if (!(freq->flags & CPUFREQ_CONST_LOOPS)) 659 mark_tsc_unstable("cpufreq changes"); 660 } 661 662 set_cyc2ns_scale(tsc_khz, freq->cpu); 663 664 return 0; 665 } Is there any specific reason for 'dummy' to exist in this function ? If not, i would like to propose the following fix. Also included fix expected by Frans Pop: > No comments on your patch, but it might be good to also fix the incorrect > indentation here: line 644 needs an extra tab. Please refer: http://lkml.org/lkml/2009/5/19/312, and, http://lkml.org/lkml/2009/5/19/301. Signed-off-by: Subrata Modak To: Cc: H. Peter Anvin Cc: Ingo Molnar Cc: Thomas Gleixner Cc: Balbir Singh Cc: Sachin P Sant Cc: Linux Kernel Cc: Andi Kleen Cc: Frans Pop Subject: [PATCH][Resend] Remove indirect variable usage at arch/x86/kernel/tsc.c --- --- a/arch/x86/kernel/tsc.c 2009-05-20 10:29:23.000000000 +0530 +++ b/arch/x86/kernel/tsc.c 2009-05-20 11:42:53.000000000 +0530 @@ -631,17 +631,16 @@ static int time_cpufreq_notifier(struct void *data) { struct cpufreq_freqs *freq = data; - unsigned long *lpj, dummy; + unsigned long *lpj = NULL; if (cpu_has(&cpu_data(freq->cpu), X86_FEATURE_CONSTANT_TSC)) return 0; - lpj = &dummy; 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; + lpj = &boot_cpu_data.loops_per_jiffy; #endif if (!ref_freq) { --- Regards-- Subrata