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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff88810335e388 of 8 bytes by interrupt on cpu 0:
 rtc_handle_legacy_irq drivers/rtc/interface.c:624 [inline]
 rtc_pie_update_irq+0x93/0xf0 drivers/rtc/interface.c:672
 __run_hrtimer kernel/time/hrtimer.c:1761 [inline]
 __hrtimer_run_queues+0x20c/0x5a0 kernel/time/hrtimer.c:1825
 hrtimer_interrupt+0x21a/0x460 kernel/time/hrtimer.c:1887
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1039 [inline]
 __sysvec_apic_timer_interrupt+0x5c/0x1d0 arch/x86/kernel/apic/apic.c:1056
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1050 [inline]
 sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1050
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:702
 __tsan_unaligned_write8+0x4/0x190 kernel/kcsan/core.c:1025
 wq_stack_add_head io_uring/slist.h:91 [inline]
 io_req_add_to_cache io_uring/io_uring.c:238 [inline]
 __io_alloc_req_refill+0x10d/0x1d0 io_uring/io_uring.c:1026
 io_alloc_req io_uring/io_uring.h:453 [inline]
 io_submit_sqes+0x892/0x1050 io_uring/io_uring.c:2386
 __do_sys_io_uring_enter io_uring/io_uring.c:3464 [inline]
 __se_sys_io_uring_enter+0x1c1/0x1b70 io_uring/io_uring.c:3398
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3398
 x64_sys_call+0x2de1/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810335e388 of 8 bytes by task 13658 on cpu 1:
 rtc_dev_poll+0x78/0xb0 drivers/rtc/dev.c:198
 vfs_poll include/linux/poll.h:82 [inline]
 __io_arm_poll_handler+0x1ee/0xb70 io_uring/poll.c:581
 io_arm_apoll+0x3d2/0x4f0 io_uring/poll.c:691
 io_arm_poll_handler+0x131/0x160 io_uring/poll.c:720
 io_queue_async+0x25b/0x450 io_uring/io_uring.c:2004
 io_queue_sqe io_uring/io_uring.c:2032 [inline]
 io_req_task_submit+0xc0/0xd0 io_uring/io_uring.c:1415
 io_handle_tw_list+0x18d/0x1c0 io_uring/io_uring.c:1102
 tctx_task_work_run+0x6d/0x1a0 io_uring/io_uring.c:1167
 tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1185
 task_work_run+0x131/0x1a0 kernel/task_work.c:227
 get_signal+0xe13/0xf70 kernel/signal.c:2807
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x7a/0x100 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000007fc0 -> 0x00000000000080c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13658 Comm: syz.8.4223 Not tainted 6.16.0-syzkaller-12245-g2988dfed8a5d #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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