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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff8881036d5388 of 8 bytes by interrupt on cpu 0:
 rtc_handle_legacy_irq drivers/rtc/interface.c:651 [inline]
 rtc_pie_update_irq+0x7b/0xd0 drivers/rtc/interface.c:699
 __run_hrtimer kernel/time/hrtimer.c:1777 [inline]
 __hrtimer_run_queues+0x20f/0x590 kernel/time/hrtimer.c:1841
 hrtimer_interrupt+0x21a/0x460 kernel/time/hrtimer.c:1903
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1d0 arch/x86/kernel/apic/apic.c:1062
 instr_sysvec_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1056 [inline]
 sysvec_apic_timer_interrupt+0x6f/0x80 arch/x86/kernel/apic/apic.c:1056
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:697
 __tsan_unaligned_write8+0x0/0x180 kernel/kcsan/core.c:753
 __tlb_adjust_range include/asm-generic/tlb.h:402 [inline]
 tlb_flush_pte_range include/asm-generic/tlb.h:618 [inline]
 tlb_remove_tlb_entries include/asm-generic/tlb.h:672 [inline]
 zap_present_folio_ptes mm/memory.c:1648 [inline]
 zap_present_ptes mm/memory.c:1712 [inline]
 do_zap_pte_range mm/memory.c:1814 [inline]
 zap_pte_range mm/memory.c:1858 [inline]
 zap_pmd_range mm/memory.c:1950 [inline]
 zap_pud_range mm/memory.c:1978 [inline]
 zap_p4d_range mm/memory.c:1999 [inline]
 unmap_page_range+0x142e/0x2590 mm/memory.c:2020
 unmap_single_vma mm/memory.c:2062 [inline]
 unmap_vmas+0x27a/0x3f0 mm/memory.c:2104
 exit_mmap+0x19e/0x6c0 mm/mmap.c:1277
 __mmput+0x28/0x1c0 kernel/fork.c:1173
 mmput+0x40/0x50 kernel/fork.c:1196
 exit_mm+0xe3/0x180 kernel/exit.c:581
 do_exit+0x3fa/0x1590 kernel/exit.c:959
 do_group_exit+0x138/0x140 kernel/exit.c:1112
 __do_sys_exit_group kernel/exit.c:1123 [inline]
 __se_sys_exit_group kernel/exit.c:1121 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1121
 x64_sys_call+0x2fff/0x3000 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881036d5388 of 8 bytes by task 16396 on cpu 1:
 rtc_dev_poll+0x78/0xb0 drivers/rtc/dev.c:198
 vfs_poll include/linux/poll.h:82 [inline]
 io_poll_check_events io_uring/poll.c:280 [inline]
 io_poll_task_func+0x13b/0x770 io_uring/poll.c:336
 io_handle_tw_list+0x121/0x230 io_uring/io_uring.c:1122
 tctx_task_work_run+0x42/0x160 io_uring/io_uring.c:1182
 tctx_task_work+0x3f/0x80 io_uring/io_uring.c:1200
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 get_signal+0xe09/0xf60 kernel/signal.c:2807
 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x1d3/0x2a0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000008fc0 -> 0x00000000000090c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 16396 Comm: syz.9.3238 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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