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BUG: KCSAN: data-race in munlock_vma_pages_range / try_to_unmap_one

write to 0xffff88808fde35c8 of 8 bytes by task 31772 on cpu 0:
 munlock_vma_pages_range+0x4f/0x6d0 mm/mlock.c:448
 munlock_vma_pages_all mm/internal.h:343 [inline]
 exit_mmap+0x128/0x3b0 mm/mmap.c:3134
 __mmput+0xa2/0x220 kernel/fork.c:1093
 mmput+0x38/0x40 kernel/fork.c:1114
 exit_mm+0x2c8/0x330 kernel/exit.c:482
 do_exit+0x415/0x16e0 kernel/exit.c:792
 do_group_exit+0x17a/0x180 kernel/exit.c:903
 __do_sys_exit_group+0xb/0x10 kernel/exit.c:914
 __se_sys_exit_group+0x5/0x10 kernel/exit.c:912
 __x64_sys_exit_group+0x16/0x20 kernel/exit.c:912
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88808fde35c8 of 8 bytes by task 31779 on cpu 1:
 try_to_unmap_one+0xae/0x1790 mm/rmap.c:1389
 rmap_walk_file+0x24a/0x4e0 mm/rmap.c:1928
 rmap_walk mm/rmap.c:1946 [inline]
 try_to_munlock+0xe7/0x150 mm/rmap.c:1797
 __munlock_isolated_page mm/mlock.c:138 [inline]
 __munlock_pagevec+0x55d/0x7d0 mm/mlock.c:346
 munlock_vma_pages_range+0x527/0x6d0 mm/mlock.c:499
 munlock_vma_pages_all mm/internal.h:343 [inline]
 exit_mmap+0x128/0x3b0 mm/mmap.c:3134
 __mmput+0xa2/0x220 kernel/fork.c:1093
 mmput+0x38/0x40 kernel/fork.c:1114
 exit_mm+0x2c8/0x330 kernel/exit.c:482
 do_exit+0x415/0x16e0 kernel/exit.c:792
 do_group_exit+0xcb/0x180 kernel/exit.c:903
 get_signal+0x106d/0x1650 kernel/signal.c:2743
 do_signal+0x25/0x270 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:235 [inline]
 __prepare_exit_to_usermode+0x127/0x230 arch/x86/entry/common.c:269
 __syscall_return_slowpath+0x47/0x60 arch/x86/entry/common.c:352
 do_syscall_64+0x5d/0xb0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 31779 Comm: syz-executor.3 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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