Messages in this thread Patch in this message | | | Date | Wed, 17 Jun 2009 15:30:46 GMT | From | tip-bot for Subrata Modak <> | Subject | [tip:x86/urgent] x86: Remove indirect variable usage at arch/x86/kernel/tsc.c |
| |
Commit-ID: 5a8aee6c809dc36e42b256566e5e28e244be3c74 Gitweb: http://git.kernel.org/tip/5a8aee6c809dc36e42b256566e5e28e244be3c74 Author: Subrata Modak <subrata@linux.vnet.ibm.com> AuthorDate: Wed, 20 May 2009 11:51:15 +0530 Committer: Ingo Molnar <mingo@elte.hu> CommitDate: Wed, 17 Jun 2009 17:26:30 +0200
x86: Remove indirect variable usage at arch/x86/kernel/tsc.c
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 }
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 <subrata@linux.vnet.ibm.com> Cc: Sachin P Sant <sachinp@linux.vnet.ibm.com> Cc: Frans Pop <elendil@planet.nl> Cc: Andi Kleen <andi@firstfloor.org> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> LKML-Reference: <20090520062115.23889.45487.sendpatchset@subratamodak.linux.ibm.com> Signed-off-by: Ingo Molnar <mingo@elte.hu>
--- arch/x86/kernel/tsc.c | 7 +++---- 1 files changed, 3 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kernel/tsc.c b/arch/x86/kernel/tsc.c index 3e1c057..7714609 100644 --- a/arch/x86/kernel/tsc.c +++ b/arch/x86/kernel/tsc.c @@ -631,17 +631,16 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, 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) { @@ -652,7 +651,7 @@ static int time_cpufreq_notifier(struct notifier_block *nb, unsigned long val, if ((val == CPUFREQ_PRECHANGE && freq->old < freq->new) || (val == CPUFREQ_POSTCHANGE && freq->old > freq->new) || (val == CPUFREQ_RESUMECHANGE)) { - *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); + *lpj = cpufreq_scale(loops_per_jiffy_ref, ref_freq, freq->new); tsc_khz = cpufreq_scale(tsc_khz_ref, ref_freq, freq->new); if (!(freq->flags & CPUFREQ_CONST_LOOPS))
| |