Hi Waiman, [auto build test WARNING on tip/auto-latest] [also build test WARNING on v4.6-rc3 next-20160411] [if your patch is applied to the wrong git tree, please drop us a note to help improving the system]
url: https://github.com/0day-ci/linux/commits/Waiman-Long/x86-hpet-Reduce-HPET-counter-read-contention/20160412-041402 config: x86_64-randconfig-x011-201615 (attached as .config) reproduce: # save the attached .config to linux build tree make ARCH=x86_64 All warnings (new ones prefixed by >>): >> arch/x86/kernel/hpet.c:786:3: warning: 'hpet_save' defined but not used >> [-Wunused-variable] } hpet_save; ^ vim +/hpet_save +786 arch/x86/kernel/hpet.c 770 * If multiple CPUs are trying to access the HPET counter at the same time, 771 * we don't actually need to read the counter multiple times. Instead, the 772 * other CPUs can use the counter value read by the first CPU in the group. 773 * 774 * A sequence number whose lsb is a lock bit is used to control which CPU 775 * has the right to read the HPET counter directly and which CPUs are going 776 * to get the indirect value read by the lock holder. For the later group, 777 * if the sequence number differs from the expected locked value, they 778 * can assume that the saved HPET value is up-to-date and return it. 779 */ 780 static struct { 781 /* Sequence number + bit lock */ 782 int seq ____cacheline_aligned_in_smp; 783 784 /* Current HPET value */ 785 u32 hpet ____cacheline_aligned_in_smp; > 786 } hpet_save; 787 #define HPET_SEQ_LOCKED(seq) ((seq) & 1) /* Odd == locked */ 788 789 /* 790 * Clock source related code 791 */ 792 #ifdef CONFIG_SMP 793 static cycle_t read_hpet(struct clocksource *cs) 794 { --- 0-DAY kernel test infrastructure Open Source Technology Center https://lists.01.org/pipermail/kbuild-all Intel Corporation
.config.gz
Description: Binary data
