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Message-ID: <202511160608.dqVtgcXd-lkp@intel.com>
Date: Sun, 16 Nov 2025 06:51:50 +0800
From: kernel test robot <lkp@...el.com>
To: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: oe-kbuild-all@...ts.linux.dev, linux-kernel@...r.kernel.org,
x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
Chen Yu <yu.c.chen@...el.com>,
Vincent Guittot <vincent.guittot@...aro.org>,
Shrikanth Hegde <sshegde@...ux.ibm.com>,
K Prateek Nayak <kprateek.nayak@....com>,
Srikar Dronamraju <srikar@...ux.ibm.com>
Subject: [tip:sched/core 11/19] kernel/sched/fair.c:11736:73: sparse: sparse:
Using plain integer as NULL pointer
tree: https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git sched/core
head: 7c983640e4db0c1fd8ce6c6cd921c19954a8d479
commit: 2265c5d4deeff3bfe4580d9ffe718fd80a414cac [11/19] sched/fair: Skip sched_balance_running cmpxchg when balance is not due
config: sparc64-randconfig-r134-20251116 (https://download.01.org/0day-ci/archive/20251116/202511160608.dqVtgcXd-lkp@intel.com/config)
compiler: sparc64-linux-gcc (GCC) 13.4.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20251116/202511160608.dqVtgcXd-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/202511160608.dqVtgcXd-lkp@intel.com/
sparse warnings: (new ones prefixed by >>)
kernel/sched/fair.c:1141:49: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct task_struct *running @@ got struct task_struct [noderef] __rcu *curr @@
kernel/sched/fair.c:1141:49: sparse: expected struct task_struct *running
kernel/sched/fair.c:1141:49: sparse: got struct task_struct [noderef] __rcu *curr
kernel/sched/fair.c:1175:33: sparse: sparse: incorrect type in argument 2 (different address spaces) @@ expected struct sched_entity *se @@ got struct sched_entity [noderef] __rcu * @@
kernel/sched/fair.c:1175:33: sparse: expected struct sched_entity *se
kernel/sched/fair.c:1175:33: sparse: got struct sched_entity [noderef] __rcu *
kernel/sched/fair.c:1231:34: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct sched_entity const *se @@ got struct sched_entity [noderef] __rcu * @@
kernel/sched/fair.c:1231:34: sparse: expected struct sched_entity const *se
kernel/sched/fair.c:1231:34: sparse: got struct sched_entity [noderef] __rcu *
kernel/sched/fair.c:12798:9: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct sched_domain *[assigned] sd @@ got struct sched_domain [noderef] __rcu *parent @@
kernel/sched/fair.c:12798:9: sparse: expected struct sched_domain *[assigned] sd
kernel/sched/fair.c:12798:9: sparse: got struct sched_domain [noderef] __rcu *parent
kernel/sched/fair.c:8347:20: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct sched_domain *[assigned] sd @@ got struct sched_domain [noderef] __rcu *parent @@
kernel/sched/fair.c:8347:20: sparse: expected struct sched_domain *[assigned] sd
kernel/sched/fair.c:8347:20: sparse: got struct sched_domain [noderef] __rcu *parent
kernel/sched/fair.c:8551:9: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct sched_domain *[assigned] tmp @@ got struct sched_domain [noderef] __rcu *parent @@
kernel/sched/fair.c:8551:9: sparse: expected struct sched_domain *[assigned] tmp
kernel/sched/fair.c:8551:9: sparse: got struct sched_domain [noderef] __rcu *parent
kernel/sched/fair.c:8684:39: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct task_struct *donor @@ got struct task_struct [noderef] __rcu *donor @@
kernel/sched/fair.c:8684:39: sparse: expected struct task_struct *donor
kernel/sched/fair.c:8684:39: sparse: got struct task_struct [noderef] __rcu *donor
kernel/sched/fair.c:8716:37: sparse: sparse: incorrect type in argument 1 (different address spaces) @@ expected struct task_struct *tsk @@ got struct task_struct [noderef] __rcu *curr @@
kernel/sched/fair.c:8716:37: sparse: expected struct task_struct *tsk
kernel/sched/fair.c:8716:37: sparse: got struct task_struct [noderef] __rcu *curr
kernel/sched/fair.c:8933:38: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct task_struct *curr @@ got struct task_struct [noderef] __rcu *donor @@
kernel/sched/fair.c:8933:38: sparse: expected struct task_struct *curr
kernel/sched/fair.c:8933:38: sparse: got struct task_struct [noderef] __rcu *donor
kernel/sched/fair.c:9969:40: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct sched_domain *child @@ got struct sched_domain [noderef] __rcu *child @@
kernel/sched/fair.c:9969:40: sparse: expected struct sched_domain *child
kernel/sched/fair.c:9969:40: sparse: got struct sched_domain [noderef] __rcu *child
kernel/sched/fair.c:10597:22: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/fair.c:10597:22: sparse: struct task_struct [noderef] __rcu *
kernel/sched/fair.c:10597:22: sparse: struct task_struct *
kernel/sched/fair.c:12068:9: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct sched_domain *[assigned] sd @@ got struct sched_domain [noderef] __rcu *parent @@
kernel/sched/fair.c:12068:9: sparse: expected struct sched_domain *[assigned] sd
kernel/sched/fair.c:12068:9: sparse: got struct sched_domain [noderef] __rcu *parent
kernel/sched/fair.c:11707:44: sparse: sparse: incorrect type in initializer (different address spaces) @@ expected struct sched_domain *sd_parent @@ got struct sched_domain [noderef] __rcu *parent @@
kernel/sched/fair.c:11707:44: sparse: expected struct sched_domain *sd_parent
kernel/sched/fair.c:11707:44: sparse: got struct sched_domain [noderef] __rcu *parent
>> kernel/sched/fair.c:11736:73: sparse: sparse: Using plain integer as NULL pointer
kernel/sched/fair.c:12168:9: sparse: sparse: incorrect type in assignment (different address spaces) @@ expected struct sched_domain *[assigned] sd @@ got struct sched_domain [noderef] __rcu *parent @@
kernel/sched/fair.c:12168:9: sparse: expected struct sched_domain *[assigned] sd
kernel/sched/fair.c:12168:9: sparse: got struct sched_domain [noderef] __rcu *parent
kernel/sched/fair.c:6679:35: sparse: sparse: marked inline, but without a definition
kernel/sched/fair.c: note: in included file:
kernel/sched/sched.h:2627:9: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/sched.h:2627:9: sparse: struct task_struct [noderef] __rcu *
kernel/sched/sched.h:2627:9: sparse: struct task_struct *
kernel/sched/sched.h:2294:26: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/sched.h:2294:26: sparse: struct task_struct [noderef] __rcu *
kernel/sched/sched.h:2294:26: sparse: struct task_struct *
kernel/sched/sched.h:2283:25: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/sched.h:2283:25: sparse: struct task_struct [noderef] __rcu *
kernel/sched/sched.h:2283:25: sparse: struct task_struct *
kernel/sched/sched.h:2294:26: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/sched.h:2294:26: sparse: struct task_struct [noderef] __rcu *
kernel/sched/sched.h:2294:26: sparse: struct task_struct *
kernel/sched/sched.h:2294:26: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/sched.h:2294:26: sparse: struct task_struct [noderef] __rcu *
kernel/sched/sched.h:2294:26: sparse: struct task_struct *
kernel/sched/sched.h:2294:26: sparse: sparse: incompatible types in comparison expression (different address spaces):
kernel/sched/sched.h:2294:26: sparse: struct task_struct [noderef] __rcu *
kernel/sched/sched.h:2294:26: sparse: struct task_struct *
vim +11736 kernel/sched/fair.c
11697
11698 /*
11699 * Check this_cpu to ensure it is balanced within domain. Attempt to move
11700 * tasks if there is an imbalance.
11701 */
11702 static int sched_balance_rq(int this_cpu, struct rq *this_rq,
11703 struct sched_domain *sd, enum cpu_idle_type idle,
11704 int *continue_balancing)
11705 {
11706 int ld_moved, cur_ld_moved, active_balance = 0;
11707 struct sched_domain *sd_parent = sd->parent;
11708 struct sched_group *group;
11709 struct rq *busiest;
11710 struct rq_flags rf;
11711 struct cpumask *cpus = this_cpu_cpumask_var_ptr(load_balance_mask);
11712 struct lb_env env = {
11713 .sd = sd,
11714 .dst_cpu = this_cpu,
11715 .dst_rq = this_rq,
11716 .dst_grpmask = group_balance_mask(sd->groups),
11717 .idle = idle,
11718 .loop_break = SCHED_NR_MIGRATE_BREAK,
11719 .cpus = cpus,
11720 .fbq_type = all,
11721 .tasks = LIST_HEAD_INIT(env.tasks),
11722 };
11723 bool need_unlock = false;
11724
11725 cpumask_and(cpus, sched_domain_span(sd), cpu_active_mask);
11726
11727 schedstat_inc(sd->lb_count[idle]);
11728
11729 redo:
11730 if (!should_we_balance(&env)) {
11731 *continue_balancing = 0;
11732 goto out_balanced;
11733 }
11734
11735 if (!need_unlock && (sd->flags & SD_SERIALIZE) && idle != CPU_NEWLY_IDLE) {
11736 if (!atomic_try_cmpxchg_acquire(&sched_balance_running, 0, 1))
11737 goto out_balanced;
11738
11739 need_unlock = true;
11740 }
11741
11742 group = sched_balance_find_src_group(&env);
11743 if (!group) {
11744 schedstat_inc(sd->lb_nobusyg[idle]);
11745 goto out_balanced;
11746 }
11747
11748 busiest = sched_balance_find_src_rq(&env, group);
11749 if (!busiest) {
11750 schedstat_inc(sd->lb_nobusyq[idle]);
11751 goto out_balanced;
11752 }
11753
11754 WARN_ON_ONCE(busiest == env.dst_rq);
11755
11756 update_lb_imbalance_stat(&env, sd, idle);
11757
11758 env.src_cpu = busiest->cpu;
11759 env.src_rq = busiest;
11760
11761 ld_moved = 0;
11762 /* Clear this flag as soon as we find a pullable task */
11763 env.flags |= LBF_ALL_PINNED;
11764 if (busiest->nr_running > 1) {
11765 /*
11766 * Attempt to move tasks. If sched_balance_find_src_group has found
11767 * an imbalance but busiest->nr_running <= 1, the group is
11768 * still unbalanced. ld_moved simply stays zero, so it is
11769 * correctly treated as an imbalance.
11770 */
11771 env.loop_max = min(sysctl_sched_nr_migrate, busiest->nr_running);
11772
11773 more_balance:
11774 rq_lock_irqsave(busiest, &rf);
11775 update_rq_clock(busiest);
11776
11777 /*
11778 * cur_ld_moved - load moved in current iteration
11779 * ld_moved - cumulative load moved across iterations
11780 */
11781 cur_ld_moved = detach_tasks(&env);
11782
11783 /*
11784 * We've detached some tasks from busiest_rq. Every
11785 * task is masked "TASK_ON_RQ_MIGRATING", so we can safely
11786 * unlock busiest->lock, and we are able to be sure
11787 * that nobody can manipulate the tasks in parallel.
11788 * See task_rq_lock() family for the details.
11789 */
11790
11791 rq_unlock(busiest, &rf);
11792
11793 if (cur_ld_moved) {
11794 attach_tasks(&env);
11795 ld_moved += cur_ld_moved;
11796 }
11797
11798 local_irq_restore(rf.flags);
11799
11800 if (env.flags & LBF_NEED_BREAK) {
11801 env.flags &= ~LBF_NEED_BREAK;
11802 goto more_balance;
11803 }
11804
11805 /*
11806 * Revisit (affine) tasks on src_cpu that couldn't be moved to
11807 * us and move them to an alternate dst_cpu in our sched_group
11808 * where they can run. The upper limit on how many times we
11809 * iterate on same src_cpu is dependent on number of CPUs in our
11810 * sched_group.
11811 *
11812 * This changes load balance semantics a bit on who can move
11813 * load to a given_cpu. In addition to the given_cpu itself
11814 * (or a ilb_cpu acting on its behalf where given_cpu is
11815 * nohz-idle), we now have balance_cpu in a position to move
11816 * load to given_cpu. In rare situations, this may cause
11817 * conflicts (balance_cpu and given_cpu/ilb_cpu deciding
11818 * _independently_ and at _same_ time to move some load to
11819 * given_cpu) causing excess load to be moved to given_cpu.
11820 * This however should not happen so much in practice and
11821 * moreover subsequent load balance cycles should correct the
11822 * excess load moved.
11823 */
11824 if ((env.flags & LBF_DST_PINNED) && env.imbalance > 0) {
11825
11826 /* Prevent to re-select dst_cpu via env's CPUs */
11827 __cpumask_clear_cpu(env.dst_cpu, env.cpus);
11828
11829 env.dst_rq = cpu_rq(env.new_dst_cpu);
11830 env.dst_cpu = env.new_dst_cpu;
11831 env.flags &= ~LBF_DST_PINNED;
11832 env.loop = 0;
11833 env.loop_break = SCHED_NR_MIGRATE_BREAK;
11834
11835 /*
11836 * Go back to "more_balance" rather than "redo" since we
11837 * need to continue with same src_cpu.
11838 */
11839 goto more_balance;
11840 }
11841
11842 /*
11843 * We failed to reach balance because of affinity.
11844 */
11845 if (sd_parent) {
11846 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
11847
11848 if ((env.flags & LBF_SOME_PINNED) && env.imbalance > 0)
11849 *group_imbalance = 1;
11850 }
11851
11852 /* All tasks on this runqueue were pinned by CPU affinity */
11853 if (unlikely(env.flags & LBF_ALL_PINNED)) {
11854 __cpumask_clear_cpu(cpu_of(busiest), cpus);
11855 /*
11856 * Attempting to continue load balancing at the current
11857 * sched_domain level only makes sense if there are
11858 * active CPUs remaining as possible busiest CPUs to
11859 * pull load from which are not contained within the
11860 * destination group that is receiving any migrated
11861 * load.
11862 */
11863 if (!cpumask_subset(cpus, env.dst_grpmask)) {
11864 env.loop = 0;
11865 env.loop_break = SCHED_NR_MIGRATE_BREAK;
11866 goto redo;
11867 }
11868 goto out_all_pinned;
11869 }
11870 }
11871
11872 if (!ld_moved) {
11873 schedstat_inc(sd->lb_failed[idle]);
11874 /*
11875 * Increment the failure counter only on periodic balance.
11876 * We do not want newidle balance, which can be very
11877 * frequent, pollute the failure counter causing
11878 * excessive cache_hot migrations and active balances.
11879 *
11880 * Similarly for migration_misfit which is not related to
11881 * load/util migration, don't pollute nr_balance_failed.
11882 */
11883 if (idle != CPU_NEWLY_IDLE &&
11884 env.migration_type != migrate_misfit)
11885 sd->nr_balance_failed++;
11886
11887 if (need_active_balance(&env)) {
11888 unsigned long flags;
11889
11890 raw_spin_rq_lock_irqsave(busiest, flags);
11891
11892 /*
11893 * Don't kick the active_load_balance_cpu_stop,
11894 * if the curr task on busiest CPU can't be
11895 * moved to this_cpu:
11896 */
11897 if (!cpumask_test_cpu(this_cpu, busiest->curr->cpus_ptr)) {
11898 raw_spin_rq_unlock_irqrestore(busiest, flags);
11899 goto out_one_pinned;
11900 }
11901
11902 /* Record that we found at least one task that could run on this_cpu */
11903 env.flags &= ~LBF_ALL_PINNED;
11904
11905 /*
11906 * ->active_balance synchronizes accesses to
11907 * ->active_balance_work. Once set, it's cleared
11908 * only after active load balance is finished.
11909 */
11910 if (!busiest->active_balance) {
11911 busiest->active_balance = 1;
11912 busiest->push_cpu = this_cpu;
11913 active_balance = 1;
11914 }
11915
11916 preempt_disable();
11917 raw_spin_rq_unlock_irqrestore(busiest, flags);
11918 if (active_balance) {
11919 stop_one_cpu_nowait(cpu_of(busiest),
11920 active_load_balance_cpu_stop, busiest,
11921 &busiest->active_balance_work);
11922 }
11923 preempt_enable();
11924 }
11925 } else {
11926 sd->nr_balance_failed = 0;
11927 }
11928
11929 if (likely(!active_balance) || need_active_balance(&env)) {
11930 /* We were unbalanced, so reset the balancing interval */
11931 sd->balance_interval = sd->min_interval;
11932 }
11933
11934 goto out;
11935
11936 out_balanced:
11937 /*
11938 * We reach balance although we may have faced some affinity
11939 * constraints. Clear the imbalance flag only if other tasks got
11940 * a chance to move and fix the imbalance.
11941 */
11942 if (sd_parent && !(env.flags & LBF_ALL_PINNED)) {
11943 int *group_imbalance = &sd_parent->groups->sgc->imbalance;
11944
11945 if (*group_imbalance)
11946 *group_imbalance = 0;
11947 }
11948
11949 out_all_pinned:
11950 /*
11951 * We reach balance because all tasks are pinned at this level so
11952 * we can't migrate them. Let the imbalance flag set so parent level
11953 * can try to migrate them.
11954 */
11955 schedstat_inc(sd->lb_balanced[idle]);
11956
11957 sd->nr_balance_failed = 0;
11958
11959 out_one_pinned:
11960 ld_moved = 0;
11961
11962 /*
11963 * sched_balance_newidle() disregards balance intervals, so we could
11964 * repeatedly reach this code, which would lead to balance_interval
11965 * skyrocketing in a short amount of time. Skip the balance_interval
11966 * increase logic to avoid that.
11967 *
11968 * Similarly misfit migration which is not necessarily an indication of
11969 * the system being busy and requires lb to backoff to let it settle
11970 * down.
11971 */
11972 if (env.idle == CPU_NEWLY_IDLE ||
11973 env.migration_type == migrate_misfit)
11974 goto out;
11975
11976 /* tune up the balancing interval */
11977 if ((env.flags & LBF_ALL_PINNED &&
11978 sd->balance_interval < MAX_PINNED_INTERVAL) ||
11979 sd->balance_interval < sd->max_interval)
11980 sd->balance_interval *= 2;
11981 out:
11982 if (need_unlock)
11983 atomic_set_release(&sched_balance_running, 0);
11984
11985 return ld_moved;
11986 }
11987
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
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