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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff8881031e7b80 of 8 bytes by interrupt on cpu 1:
 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
 preempt_count arch/x86/include/asm/preempt.h:27 [inline]
 get_ctx kernel/kcsan/core.c:206 [inline]
 check_access kernel/kcsan/core.c:750 [inline]
 __tsan_read8+0xbe/0x190 kernel/kcsan/core.c:1025
 folio_test_anon include/linux/page-flags.h:732 [inline]
 mm_counter include/linux/mm.h:2609 [inline]
 zap_present_folio_ptes mm/memory.c:1515 [inline]
 zap_present_ptes mm/memory.c:1590 [inline]
 do_zap_pte_range mm/memory.c:1691 [inline]
 zap_pte_range mm/memory.c:1735 [inline]
 zap_pmd_range mm/memory.c:1827 [inline]
 zap_pud_range mm/memory.c:1856 [inline]
 zap_p4d_range mm/memory.c:1877 [inline]
 unmap_page_range+0x13de/0x2740 mm/memory.c:1898
 unmap_single_vma mm/memory.c:1941 [inline]
 unmap_vmas+0x23d/0x3a0 mm/memory.c:1985
 exit_mmap+0x1b0/0x6c0 mm/mmap.c:1284
 __mmput+0x28/0x1c0 kernel/fork.c:1121
 mmput+0x40/0x50 kernel/fork.c:1144
 exit_mm+0xe4/0x190 kernel/exit.c:581
 do_exit+0x417/0x1590 kernel/exit.c:952
 do_group_exit+0x139/0x140 kernel/exit.c:1105
 __do_sys_exit_group kernel/exit.c:1116 [inline]
 __se_sys_exit_group kernel/exit.c:1114 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1114
 x64_sys_call+0x2fa4/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:232
 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 0xffff8881031e7b80 of 8 bytes by task 17496 on cpu 0:
 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_poll_handler+0x427/0x590 io_uring/poll.c:706
 io_queue_async+0x60/0x3a0 io_uring/io_uring.c:1949
 io_queue_sqe io_uring/io_uring.c:1975 [inline]
 io_req_task_submit+0xbb/0xc0 io_uring/io_uring.c:1380
 io_handle_tw_list+0x190/0x1c0 io_uring/io_uring.c:1067
 tctx_task_work_run+0x6d/0x1a0 io_uring/io_uring.c:1132
 tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1150
 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:111
 exit_to_user_mode_prepare include/linux/entry-common.h:330 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:414 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:449 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000003bc0 -> 0x0000000000003cc0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 17496 Comm: syz.1.5793 Not tainted 6.16.0-rc6-syzkaller-00253-g4871b7cb27f4 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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