Re: [PATCH v4 1/1] printk: fix zero-valued printk timestamps in early boot

kernel test robot
2026-04-12T10:11:39Z

Hi Tim,

kernel test robot noticed the following build warnings:

[auto build test WARNING on linus/master]
[also build test WARNING on v7.0-rc7 next-20260410]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url: https://github.com/intel-lab-lkp/linux/commits/Tim-Bird/printk-fix-zero-valued-printk-timestamps-in-early-boot/20260412-134726
base: linus/master
patch link: https://lore.kernel.org/r/20260410203741.997410-2-tim.bird%40sony.com
patch subject: [PATCH v4 1/1] printk: fix zero-valued printk timestamps in early boot
config: arm64-allnoconfig (https://download.01.org/0day-ci/archive/20260412/202604121822.OvOLcTnO-lkp@intel.com/config)
compiler: aarch64-linux-gcc (GCC) 15.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260412/202604121822.OvOLcTnO-lkp@intel.com/reproduce)

If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202604121822.OvOLcTnO-lkp@intel.com/

All warnings (new ones prefixed by >>):

In file included from kernel/printk/printk.c:49:
include/linux/early_times.h: In function 'early_times_ns':
>> include/linux/early_times.h:45:61: warning: division by zero [-Wdiv-by-zero]
45 | return (early_unsafe_cycles() * NS_PER_KHZ) / CONFIG_EARLY_CYCLES_KHZ;
| ^

vim +45 include/linux/early_times.h

34
35 /* returns a nanosecond value based on early cycles */
36 static inline u64 early_times_ns(void)
37 {
38 if (CONFIG_EARLY_CYCLES_KHZ)
39 /*
40 * Note: the multiply must precede the division to avoid
41 * truncation and loss of resolution
42 * Don't use fancier MULT/SHIFT math here. Since this is
43 * static, the compiler can optimize the math operations.
44 */
> 45 return (early_unsafe_cycles() * NS_PER_KHZ) / CONFIG_EARLY_CYCLES_KHZ;
46 return 0;
47 }
48 #else
49 static inline u64 early_times_ns(void)
50 {
51 return 0;
52 }
53 #endif
54

--
0-DAY CI Kernel Test Service