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BUG: KCSAN: data-race in hrtimer_interrupt / print_cpu

read-write to 0xffff88813bd1de9a of 2 bytes by interrupt on cpu 1:
 hrtimer_interrupt+0x8f9/0xa10 kernel/time/hrtimer.c:1687
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1085 [inline]
 __sysvec_apic_timer_interrupt+0x6f/0x200 arch/x86/kernel/apic/apic.c:1102
 asm_call_irq_on_stack+0xf/0x20
 __run_sysvec_on_irqstack arch/x86/include/asm/irq_stack.h:37 [inline]
 run_sysvec_on_irqstack_cond arch/x86/include/asm/irq_stack.h:89 [inline]
 sysvec_apic_timer_interrupt+0x52/0x90 arch/x86/kernel/apic/apic.c:1096
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:628
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:94 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:169 [inline]
 _raw_spin_unlock_irq+0x2c/0x40 kernel/locking/spinlock.c:199
 finish_lock_switch kernel/sched/core.c:4065 [inline]
 finish_task_switch+0xc0/0x2a0 kernel/sched/core.c:4182
 context_switch kernel/sched/core.c:4316 [inline]
 __schedule+0x3c1/0x580 kernel/sched/core.c:5064
 preempt_schedule_common kernel/sched/core.c:5224 [inline]
 preempt_schedule+0x54/0x80 kernel/sched/core.c:5249
 preempt_schedule_thunk+0x16/0x18 arch/x86/entry/thunk_64.S:40
 __raw_spin_unlock_irqrestore include/linux/spinlock_api_smp.h:161 [inline]
 _raw_spin_unlock_irqrestore+0x48/0x50 kernel/locking/spinlock.c:191
 rcu_preempt_deferred_qs_irqrestore+0x396/0x570 kernel/rcu/tree.c:2229
 rcu_read_unlock_special kernel/rcu/tree_plugin.h:643 [inline]
 __rcu_read_unlock+0xba/0x250 kernel/rcu/tree_plugin.h:399
 rcu_read_unlock include/linux/rcupdate.h:701 [inline]
 unlocked_inode_to_wb_end include/linux/backing-dev.h:338 [inline]
 clear_page_dirty_for_io+0x278/0x300 mm/page-writeback.c:2715
 mpage_submit_page fs/ext4/inode.c:2081 [inline]
 mpage_process_page_bufs+0x41e/0x5d0 fs/ext4/inode.c:2215
 mpage_prepare_extent_to_map+0x4d6/0x630 fs/ext4/inode.c:2627
 ext4_writepages+0x674/0x1e50 fs/ext4/inode.c:2755
 do_writepages+0x7b/0x150 mm/page-writeback.c:2352
 __filemap_fdatawrite_range+0x19d/0x1d0 mm/filemap.c:422
 file_write_and_wait_range+0x9f/0x120 mm/filemap.c:761
 ext4_sync_file+0x105/0x6e0 fs/ext4/fsync.c:151
 vfs_fsync_range+0x107/0x120 fs/sync.c:200
 generic_write_sync include/linux/fs.h:2737 [inline]
 ext4_buffered_write_iter+0x384/0x3d0 fs/ext4/file.c:278
 ext4_file_write_iter+0x45e/0x1090 fs/ext4/file.c:503
 call_write_iter include/linux/fs.h:1901 [inline]
 do_iter_readv_writev+0x2cb/0x360 fs/read_write.c:740
 do_iter_write+0x112/0x4b0 fs/read_write.c:866
 vfs_iter_write+0x4c/0x70 fs/read_write.c:907
 iter_file_splice_write+0x42a/0x780 fs/splice.c:686
 do_splice_from fs/splice.c:764 [inline]
 direct_splice_actor+0x80/0xa0 fs/splice.c:933
 splice_direct_to_actor+0x345/0x650 fs/splice.c:888
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1312 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xa9/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88813bd1de9a of 2 bytes by task 21817 on cpu 0:
 print_cpu+0x3c8/0x690 kernel/time/timer_list.c:137
 timer_list_show+0x114/0x180 kernel/time/timer_list.c:283
 seq_read_iter+0x2d8/0x8e0 fs/seq_file.c:227
 proc_reg_read_iter+0xfc/0x170 fs/proc/inode.c:310
 call_read_iter include/linux/fs.h:1895 [inline]
 generic_file_splice_read+0x22a/0x310 fs/splice.c:311
 do_splice_to fs/splice.c:788 [inline]
 splice_direct_to_actor+0x2aa/0x650 fs/splice.c:867
 do_splice_direct+0xf5/0x170 fs/splice.c:976
 do_sendfile+0x5db/0xca0 fs/read_write.c:1257
 __do_sys_sendfile64 fs/read_write.c:1318 [inline]
 __se_sys_sendfile64 fs/read_write.c:1304 [inline]
 __x64_sys_sendfile64+0xf2/0x130 fs/read_write.c:1304
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 21817 Comm: syz-executor.4 Not tainted 5.11.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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