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BUG: KCSAN: data-race in run_timer_softirq / try_to_del_timer_sync

write to 0xffff88812c11dc88 of 8 bytes by interrupt on cpu 1:
 expire_timers kernel/time/timer.c:1451 [inline]
 __run_timers kernel/time/timer.c:1774 [inline]
 __run_timers kernel/time/timer.c:1741 [inline]
 run_timer_softirq+0xb1c/0xbd0 kernel/time/timer.c:1787
 __do_softirq+0x118/0x34a kernel/softirq.c:292
 invoke_softirq kernel/softirq.c:373 [inline]
 irq_exit+0xb5/0xd0 kernel/softirq.c:413
 exiting_irq arch/x86/include/asm/apic.h:546 [inline]
 smp_apic_timer_interrupt+0xe2/0x270 arch/x86/kernel/apic/apic.c:1140
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 preempt_count arch/x86/include/asm/preempt.h:26 [inline]
 get_ctx kernel/kcsan/core.c:193 [inline]
 check_access kernel/kcsan/core.c:579 [inline]
 __tsan_unaligned_write4+0x6f/0x110 kernel/kcsan/core.c:769
 rcu_preempt_read_enter kernel/rcu/tree_plugin.h:355 [inline]
 __rcu_read_lock+0x3c/0x50 kernel/rcu/tree_plugin.h:375
 rcu_read_lock include/linux/rcupdate.h:599 [inline]
 percpu_ref_put_many include/linux/percpu-refcount.h:304 [inline]
 percpu_ref_put include/linux/percpu-refcount.h:325 [inline]
 blk_queue_exit block/blk-core.c:445 [inline]
 generic_make_request block/blk-core.c:1077 [inline]
 generic_make_request+0x1a6/0x700 block/blk-core.c:1017
 submit_bio+0x8f/0x3a0 block/blk-core.c:1200
 submit_bio_wait+0xaf/0x150 block/bio.c:1077
 blkdev_issue_flush+0x12a/0x190 block/blk-flush.c:461
 ext4_sync_file+0x64d/0x8b0 fs/ext4/fsync.c:179
 vfs_fsync_range+0x7c/0x150 fs/sync.c:197
 generic_write_sync include/linux/fs.h:2872 [inline]
 ext4_buffered_write_iter+0x211/0x280 fs/ext4/file.c:277
 ext4_file_write_iter+0xf4/0xd30 fs/ext4/file.c:642
 call_write_iter include/linux/fs.h:1907 [inline]
 do_iter_readv_writev+0x4a7/0x5d0 fs/read_write.c:694
 do_iter_write fs/read_write.c:999 [inline]
 do_iter_write+0x137/0x3a0 fs/read_write.c:980
 vfs_iter_write+0x56/0x80 fs/read_write.c:1040
 iter_file_splice_write+0x530/0x830 fs/splice.c:760
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x380/0x800 fs/read_write.c:1521
 __do_sys_sendfile64 fs/read_write.c:1576 [inline]
 __se_sys_sendfile64 fs/read_write.c:1568 [inline]
 __x64_sys_sendfile64+0xb8/0x140 fs/read_write.c:1568
 do_syscall_64+0xc7/0x3b0 arch/x86/entry/common.c:295
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88812c11dc88 of 8 bytes by task 10 on cpu 0:
 try_to_del_timer_sync+0x40/0xb0 kernel/time/timer.c:1226
 del_timer_sync+0x68/0xa0 kernel/time/timer.c:1366
 schedule_timeout+0x106/0x280 kernel/time/timer.c:1899
 rcu_gp_fqs_loop+0x34c/0x540 kernel/rcu/tree.c:1674
 rcu_gp_kthread+0x113/0x1e0 kernel/rcu/tree.c:1836
 kthread+0x203/0x230 kernel/kthread.c:268
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10 Comm: rcu_preempt Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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