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BUG: KCSAN: data-race in kcompactd / kthread_is_per_cpu

write to 0xffff888100a0a0ac of 4 bytes by task 472 on cpu 1:
 freezer_do_not_count include/linux/freezer.h:109 [inline]
 freezable_schedule_timeout include/linux/freezer.h:191 [inline]
 kcompactd+0x33e/0xc10 mm/compaction.c:2906
 kthread+0x1d0/0x1f0 kernel/kthread.c:313
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:294

read to 0xffff888100a0a0ac of 4 bytes by interrupt on cpu 0:
 __to_kthread kernel/kthread.c:101 [inline]
 kthread_is_per_cpu+0x2d/0x80 kernel/kthread.c:540
 can_migrate_task+0xf/0x180 kernel/sched/fair.c:7615
 detach_tasks+0xab/0x380 kernel/sched/fair.c:7779
 load_balance+0x768/0xcc0 kernel/sched/fair.c:9679
 rebalance_domains+0x1ae/0x2d0 kernel/sched/fair.c:10058
 __do_softirq+0x12c/0x275 kernel/softirq.c:559
 invoke_softirq kernel/softirq.c:433 [inline]
 __irq_exit_rcu+0xa5/0xb0 kernel/softirq.c:637
 sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:647
 smap_restore arch/x86/include/asm/smap.h:67 [inline]
 kcsan_setup_watchpoint+0x369/0x380 kernel/kcsan/core.c:584
 sb_find_get_block include/linux/buffer_head.h:340 [inline]
 recently_deleted fs/ext4/ialloc.c:686 [inline]
 find_inode_bit+0x173/0x330 fs/ext4/ialloc.c:728
 __ext4_new_inode+0xc7a/0x2f70 fs/ext4/ialloc.c:1063
 ext4_symlink+0x2c3/0x700 fs/ext4/namei.c:3463
 vfs_symlink+0x23a/0x300 fs/namei.c:4172
 do_symlinkat+0xeb/0x280 fs/namei.c:4202
 __do_sys_symlink fs/namei.c:4223 [inline]
 __se_sys_symlink fs/namei.c:4221 [inline]
 __x64_sys_symlink+0x32/0x40 fs/namei.c:4221
 do_syscall_64+0x4a/0x90 arch/x86/entry/common.c:47
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00200040 -> 0x40200040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6804 Comm: syz-executor.4 Not tainted 5.13.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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