Re: [PATCH] kernel/sched/fair: Fix the issue of virtual runtime conversion error

[kernel test robot <lkp@intel.com>]

Hi Li,

kernel test robot noticed the following build errors:

[auto build test ERROR on tip/sched/core]
[also build test ERROR on peterz-queue/sched/core linus/master v7.1-rc5 next-20260526]
[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/Li-kunyu/kernel-sched-fair-Fix-the-issue-of-virtual-runtime-conversion-error/20260526-151853
base:   tip/sched/core
patch link:    https://lore.kernel.org/r/20260526071537.17460-1-likunyu10%40163.com
patch subject: [PATCH] kernel/sched/fair: Fix the issue of virtual runtime conversion error
config: i386-allnoconfig-bpf (https://download.01.org/0day-ci/archive/20260527/202605270352.wVynZOtB-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260527/202605270352.wVynZOtB-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/202605270352.wVynZOtB-lkp@intel.com/

All errors (new ones prefixed by >>):

   ld: kernel/sched/fair.o: in function `hrtick_start_fair':
>> kernel/sched/fair.c:7633:(.text+0x701): undefined reference to `__udivdi3'


vim +7633 kernel/sched/fair.c

  7603	
  7604	/**************************************************
  7605	 * CFS operations on tasks:
  7606	 */
  7607	
  7608	#ifdef CONFIG_SCHED_HRTICK
  7609	static void hrtick_start_fair(struct rq *rq, struct task_struct *p)
  7610	{
  7611		struct sched_entity *se = &p->se;
  7612		unsigned long scale = 1024;
  7613		unsigned long util = 0;
  7614		u64 vdelta;
  7615		u64 delta;
  7616	
  7617		WARN_ON_ONCE(task_rq(p) != rq);
  7618	
  7619		if (rq->cfs.h_nr_queued <= 1)
  7620			return;
  7621	
  7622		/*
  7623		 * Compute time until virtual deadline
  7624		 */
  7625		vdelta = se->deadline - se->vruntime;
  7626		if ((s64)vdelta < 0) {
  7627			if (task_current_donor(rq, p))
  7628				resched_curr(rq);
  7629			return;
  7630		}
  7631	
  7632		if (unlikely(se->load.weight != NICE_0_LOAD))
> 7633			delta = (NICE_0_LOAD * vdelta) / se->load.weight;
  7634	
  7635		/*
  7636		 * Correct for instantaneous load of other classes.
  7637		 */
  7638		util += cpu_util_irq(rq);
  7639		if (util && util < 1024) {
  7640			scale *= 1024;
  7641			scale /= (1024 - util);
  7642		}
  7643	
  7644		hrtick_start(rq, (scale * delta) / 1024);
  7645	}
  7646	

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