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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff888102bf7388 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:1785 [inline]
 __hrtimer_run_queues+0x218/0x4f0 kernel/time/hrtimer.c:1849
 hrtimer_interrupt+0x269/0x810 kernel/time/hrtimer.c:1911
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1045 [inline]
 __sysvec_apic_timer_interrupt+0x5f/0x1f0 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
 native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
 pv_native_safe_halt+0xf/0x20 arch/x86/kernel/paravirt.c:62
 arch_safe_halt arch/x86/kernel/process.c:766 [inline]
 default_idle+0x9/0x20 arch/x86/kernel/process.c:767
 default_idle_call+0x3b/0x60 kernel/sched/idle.c:122
 cpuidle_idle_call kernel/sched/idle.c:191 [inline]
 do_idle+0xcd/0x230 kernel/sched/idle.c:332
 cpu_startup_entry+0x24/0x30 kernel/sched/idle.c:430
 rest_init+0xee/0xf0 init/main.c:760
 start_kernel+0x49a/0x4c0 init/main.c:1210
 x86_64_start_reservations+0x24/0x30 arch/x86/kernel/head64.c:310
 x86_64_start_kernel+0xfc/0x100 arch/x86/kernel/head64.c:291
 common_startup_64+0x13e/0x147

read to 0xffff888102bf7388 of 8 bytes by task 2241 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+0x1ec/0xc30 io_uring/poll.c:581
 io_poll_add+0x69/0xf0 io_uring/poll.c:899
 __io_issue_sqe+0xfd/0x2d0 io_uring/io_uring.c:1384
 io_issue_sqe+0x206/0xc00 io_uring/io_uring.c:1407
 io_queue_sqe io_uring/io_uring.c:1634 [inline]
 io_submit_sqe io_uring/io_uring.c:1920 [inline]
 io_submit_sqes+0x7fb/0x1270 io_uring/io_uring.c:2043
 __do_sys_io_uring_enter io_uring/io_uring.c:2603 [inline]
 __se_sys_io_uring_enter+0x1c9/0xf50 io_uring/io_uring.c:2538
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:2538
 x64_sys_call+0x1e16/0x3020 arch/x86/include/generated/asm/syscalls_64.h:427
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000000009c0 -> 0x0000000000000ac0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2241 Comm: syz.8.12731 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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