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BUG: KCSAN: data-race in expire_timers / try_to_del_timer_sync

write to 0xffff888237d376c8 of 8 bytes by interrupt on cpu 1:
 expire_timers+0x13d/0x250 kernel/time/timer.c:1463
 __run_timers+0x358/0x420 kernel/time/timer.c:1731
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1744
 __do_softirq+0x12c/0x26e kernel/softirq.c:558
 invoke_softirq kernel/softirq.c:432 [inline]
 __irq_exit_rcu+0x9a/0xb0 kernel/softirq.c:636
 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:638
 __list_del_entry_valid+0x45/0xc0 lib/list_debug.c:51
 __list_del_entry include/linux/list.h:132 [inline]
 list_del_init include/linux/list.h:204 [inline]
 inode_cgwb_move_to_attached+0x8f/0x1f0 fs/fs-writeback.c:1162
 writeback_single_inode+0x2cd/0x3c0 fs/fs-writeback.c:1735
 sync_inode fs/fs-writeback.c:2742 [inline]
 sync_inode_metadata+0x57/0x80 fs/fs-writeback.c:2762
 ext4_fsync_nojournal fs/ext4/fsync.c:92 [inline]
 ext4_sync_file+0x359/0x670 fs/ext4/fsync.c:170
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2987 [inline]
 ext4_buffered_write_iter+0x39c/0x3f0 fs/ext4/file.c:277
 ext4_file_write_iter+0x2e7/0x11d0 fs/ext4/file.c:519
 call_write_iter include/linux/fs.h:2114 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4c0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x40a/0x750 fs/splice.c:689
 do_splice_from fs/splice.c:767 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:936
 splice_direct_to_actor+0x345/0x650 fs/splice.c:891
 do_splice_direct+0xf5/0x170 fs/splice.c:979
 do_sendfile+0x773/0xda0 fs/read_write.c:1260
 __do_sys_sendfile64 fs/read_write.c:1325 [inline]
 __se_sys_sendfile64 fs/read_write.c:1311 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1311
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237d376c8 of 8 bytes by task 11 on cpu 0:
 try_to_del_timer_sync+0xe3/0x290 kernel/time/timer.c:1231
 del_timer_sync kernel/time/timer.c:1378 [inline]
 schedule_timeout+0x108/0x240 kernel/time/timer.c:1879
 rcu_gp_fqs_loop kernel/rcu/tree.c:1996 [inline]
 rcu_gp_kthread+0xbf7/0xec0 kernel/rcu/tree.c:2169
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

value changed: 0xffffc90000277e60 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11 Comm: rcu_sched Not tainted 5.14.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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