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BUG: KCSAN: data-race in osq_lock / osq_lock

write to 0xffff88812be2b054 of 4 bytes by task 15531 on cpu 0:
 osq_lock+0x89/0x2f0 kernel/locking/osq_lock.c:99
 rwsem_optimistic_spin+0x5f/0x320 kernel/locking/rwsem.c:800
 rwsem_down_write_slowpath+0x109/0x950 kernel/locking/rwsem.c:1150
 __down_write kernel/locking/rwsem.c:1392 [inline]
 down_write+0x88/0x90 kernel/locking/rwsem.c:1535
 anon_vma_lock_write include/linux/rmap.h:120 [inline]
 anon_vma_free mm/rmap.c:120 [inline]
 __put_anon_vma+0x14e/0x1a0 mm/rmap.c:1770
 put_anon_vma include/linux/rmap.h:115 [inline]
 unlink_anon_vmas+0x420/0x4b0 mm/rmap.c:416
 free_pgtables+0x147/0x200 mm/memory.c:395
 exit_mmap+0x151/0x300 mm/mmap.c:3162
 __mmput kernel/fork.c:1079 [inline]
 mmput+0xea/0x280 kernel/fork.c:1100
 exit_mm kernel/exit.c:485 [inline]
 do_exit+0x4c9/0x18f0 kernel/exit.c:804
 do_group_exit+0xb4/0x1c0 kernel/exit.c:921
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x3b/0xc00 arch/x86/kernel/signal.c:815
 exit_to_usermode_loop+0x250/0x2c0 arch/x86/entry/common.c:159

read to 0xffff88812be2b054 of 4 bytes by task 16576 on cpu 1:
 osq_lock+0x170/0x2f0 kernel/locking/osq_lock.c:143
 rwsem_optimistic_spin+0x5f/0x320 kernel/locking/rwsem.c:800
 rwsem_down_write_slowpath+0x109/0x950 kernel/locking/rwsem.c:1150
 __down_write kernel/locking/rwsem.c:1392 [inline]
 down_write+0x88/0x90 kernel/locking/rwsem.c:1535
 anon_vma_lock_write include/linux/rmap.h:120 [inline]
 anon_vma_free mm/rmap.c:120 [inline]
 __put_anon_vma+0x14e/0x1a0 mm/rmap.c:1770
 put_anon_vma include/linux/rmap.h:115 [inline]
 unlink_anon_vmas+0x420/0x4b0 mm/rmap.c:416
 free_pgtables+0x147/0x200 mm/memory.c:395
 exit_mmap+0x151/0x300 mm/mmap.c:3162
 __mmput kernel/fork.c:1079 [inline]
 mmput+0xea/0x280 kernel/fork.c:1100
 exit_mm kernel/exit.c:485 [inline]
 do_exit+0x4c9/0x18f0 kernel/exit.c:804
 do_group_exit+0xb4/0x1c0 kernel/exit.c:921
 get_signal+0x2a2/0x1320 kernel/signal.c:2734
 do_signal+0x3b/0xc00 arch/x86/kernel/signal.c:815

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 16576 Comm: syz-executor.2 Not tainted 5.4.0-rc3+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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