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Message-ID: <202511141344.rntAQaRB-lkp@intel.com>
Date: Fri, 14 Nov 2025 14:47:39 +0800
From: kernel test robot <lkp@...el.com>
To: Tvrtko Ursulin <tvrtko.ursulin@...lia.com>,
linux-kernel@...r.kernel.org
Cc: llvm@...ts.linux.dev, oe-kbuild-all@...ts.linux.dev,
kernel-dev@...lia.com, Tvrtko Ursulin <tvrtko.ursulin@...lia.com>,
Johannes Weiner <hannes@...xchg.org>,
Suren Baghdasaryan <surenb@...gle.com>,
Peter Ziljstra <peterz@...radead.org>
Subject: Re: [PATCH] sched/psi: Streamline the flow in psi_group_change
Hi Tvrtko,
kernel test robot noticed the following build warnings:
[auto build test WARNING on tip/sched/core]
[also build test WARNING on linus/master v6.18-rc5 next-20251113]
[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/Tvrtko-Ursulin/sched-psi-Streamline-the-flow-in-psi_group_change/20251113-203009
base: tip/sched/core
patch link: https://lore.kernel.org/r/20251113122254.40445-1-tvrtko.ursulin%40igalia.com
patch subject: [PATCH] sched/psi: Streamline the flow in psi_group_change
config: arm-randconfig-003-20251114 (https://download.01.org/0day-ci/archive/20251114/202511141344.rntAQaRB-lkp@intel.com/config)
compiler: clang version 22.0.0git (https://github.com/llvm/llvm-project 0bba1e76581bad04e7d7f09f5115ae5e2989e0d9)
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251114/202511141344.rntAQaRB-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@...el.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202511141344.rntAQaRB-lkp@intel.com/
All warnings (new ones prefixed by >>):
In file included from kernel/sched/build_utility.c:93:
>> kernel/sched/psi.c:855:42: warning: variable 'state_mask' is uninitialized when used here [-Wuninitialized]
855 | state_mask = test_states(groupc->tasks, state_mask);
| ^~~~~~~~~~
kernel/sched/psi.c:802:16: note: initialize the variable 'state_mask' to silence this warning
802 | u32 state_mask;
| ^
| = 0
1 warning generated.
vim +/state_mask +855 kernel/sched/psi.c
eb414681d5a07d Johannes Weiner 2018-10-26 792
570c8efd5eb79c Peter Zijlstra 2025-05-23 793 #define for_each_group(iter, group) \
570c8efd5eb79c Peter Zijlstra 2025-05-23 794 for (typeof(group) iter = group; iter; iter = iter->parent)
570c8efd5eb79c Peter Zijlstra 2025-05-23 795
36b238d5717279 Johannes Weiner 2020-03-16 796 static void psi_group_change(struct psi_group *group, int cpu,
3840cbe24cf060 Johannes Weiner 2024-10-03 797 unsigned int clear, unsigned int set,
570c8efd5eb79c Peter Zijlstra 2025-05-23 798 u64 now, bool wake_clock)
eb414681d5a07d Johannes Weiner 2018-10-26 799 {
eb414681d5a07d Johannes Weiner 2018-10-26 800 struct psi_group_cpu *groupc;
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 801 unsigned long t, m;
71dbdde7914d32 Johannes Weiner 2022-08-26 802 u32 state_mask;
eb414681d5a07d Johannes Weiner 2018-10-26 803
ddae0ca2a8fe12 John Stultz 2024-06-18 804 lockdep_assert_rq_held(cpu_rq(cpu));
eb414681d5a07d Johannes Weiner 2018-10-26 805 groupc = per_cpu_ptr(group->pcpu, cpu);
eb414681d5a07d Johannes Weiner 2018-10-26 806
71dbdde7914d32 Johannes Weiner 2022-08-26 807 /*
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 808 * TSK_ONCPU does not have a corresponding task count - it's just a
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 809 * boolean flag directly encoded in the state mask. Clear, set, or carry
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 810 * the current state if no changes are requested.
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 811 *
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 812 * The rest of the state mask is calculated based on the task counts.
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 813 * Update those first, then construct the mask.
71dbdde7914d32 Johannes Weiner 2022-08-26 814 */
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 815 m = clear;
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 816 for_each_set_bit(t, &m, ARRAY_SIZE(groupc->tasks)) {
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 817 if (likely(groupc->tasks[t])) {
9d10a13d1e4c34 Charan Teja Reddy 2021-04-16 818 groupc->tasks[t]--;
9d10a13d1e4c34 Charan Teja Reddy 2021-04-16 819 } else if (!psi_bug) {
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 820 printk_deferred(KERN_ERR "psi: task underflow! cpu=%d t=%lu tasks=[%u %u %u %u] clear=%x set=%x\n",
eb414681d5a07d Johannes Weiner 2018-10-26 821 cpu, t, groupc->tasks[0],
eb414681d5a07d Johannes Weiner 2018-10-26 822 groupc->tasks[1], groupc->tasks[2],
71dbdde7914d32 Johannes Weiner 2022-08-26 823 groupc->tasks[3], clear, set);
eb414681d5a07d Johannes Weiner 2018-10-26 824 psi_bug = 1;
eb414681d5a07d Johannes Weiner 2018-10-26 825 }
eb414681d5a07d Johannes Weiner 2018-10-26 826 }
eb414681d5a07d Johannes Weiner 2018-10-26 827
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 828 m = set;
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 829 for_each_set_bit(t, &m, ARRAY_SIZE(groupc->tasks))
eb414681d5a07d Johannes Weiner 2018-10-26 830 groupc->tasks[t]++;
eb414681d5a07d Johannes Weiner 2018-10-26 831
34f26a15611afb Chengming Zhou 2022-09-07 832 if (!group->enabled) {
34f26a15611afb Chengming Zhou 2022-09-07 833 /*
34f26a15611afb Chengming Zhou 2022-09-07 834 * On the first group change after disabling PSI, conclude
34f26a15611afb Chengming Zhou 2022-09-07 835 * the current state and flush its time. This is unlikely
34f26a15611afb Chengming Zhou 2022-09-07 836 * to matter to the user, but aggregation (get_recent_times)
34f26a15611afb Chengming Zhou 2022-09-07 837 * may have already incorporated the live state into times_prev;
34f26a15611afb Chengming Zhou 2022-09-07 838 * avoid a delta sample underflow when PSI is later re-enabled.
34f26a15611afb Chengming Zhou 2022-09-07 839 */
34f26a15611afb Chengming Zhou 2022-09-07 840 if (unlikely(groupc->state_mask & (1 << PSI_NONIDLE)))
34f26a15611afb Chengming Zhou 2022-09-07 841 record_times(groupc, now);
34f26a15611afb Chengming Zhou 2022-09-07 842
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 843 if (unlikely(clear & TSK_ONCPU))
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 844 state_mask = 0;
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 845 else if (unlikely(set & TSK_ONCPU))
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 846 state_mask = PSI_ONCPU;
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 847 else
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 848 state_mask = groupc->state_mask & PSI_ONCPU;
c6ccdabec91131 Tvrtko Ursulin 2025-11-13 849
34f26a15611afb Chengming Zhou 2022-09-07 850 groupc->state_mask = state_mask;
34f26a15611afb Chengming Zhou 2022-09-07 851
34f26a15611afb Chengming Zhou 2022-09-07 852 return;
34f26a15611afb Chengming Zhou 2022-09-07 853 }
34f26a15611afb Chengming Zhou 2022-09-07 854
0ec208ce983492 Tvrtko Ursulin 2024-06-25 @855 state_mask = test_states(groupc->tasks, state_mask);
7fae6c8171d20a Chengming Zhou 2021-03-03 856
7fae6c8171d20a Chengming Zhou 2021-03-03 857 /*
7fae6c8171d20a Chengming Zhou 2021-03-03 858 * Since we care about lost potential, a memstall is FULL
7fae6c8171d20a Chengming Zhou 2021-03-03 859 * when there are no other working tasks, but also when
7fae6c8171d20a Chengming Zhou 2021-03-03 860 * the CPU is actively reclaiming and nothing productive
7fae6c8171d20a Chengming Zhou 2021-03-03 861 * could run even if it were runnable. So when the current
7fae6c8171d20a Chengming Zhou 2021-03-03 862 * task in a cgroup is in_memstall, the corresponding groupc
7fae6c8171d20a Chengming Zhou 2021-03-03 863 * on that cpu is in PSI_MEM_FULL state.
7fae6c8171d20a Chengming Zhou 2021-03-03 864 */
71dbdde7914d32 Johannes Weiner 2022-08-26 865 if (unlikely((state_mask & PSI_ONCPU) && cpu_curr(cpu)->in_memstall))
7fae6c8171d20a Chengming Zhou 2021-03-03 866 state_mask |= (1 << PSI_MEM_FULL);
7fae6c8171d20a Chengming Zhou 2021-03-03 867
34f26a15611afb Chengming Zhou 2022-09-07 868 record_times(groupc, now);
34f26a15611afb Chengming Zhou 2022-09-07 869
33b2d6302abc4c Suren Baghdasaryan 2019-05-14 870 groupc->state_mask = state_mask;
33b2d6302abc4c Suren Baghdasaryan 2019-05-14 871
65457b74aa9437 Domenico Cerasuolo 2023-03-30 872 if (state_mask & group->rtpoll_states)
65457b74aa9437 Domenico Cerasuolo 2023-03-30 873 psi_schedule_rtpoll_work(group, 1, false);
36b238d5717279 Johannes Weiner 2020-03-16 874
36b238d5717279 Johannes Weiner 2020-03-16 875 if (wake_clock && !delayed_work_pending(&group->avgs_work))
36b238d5717279 Johannes Weiner 2020-03-16 876 schedule_delayed_work(&group->avgs_work, PSI_FREQ);
eb414681d5a07d Johannes Weiner 2018-10-26 877 }
eb414681d5a07d Johannes Weiner 2018-10-26 878
--
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