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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff888103450b88 of 8 bytes by interrupt on cpu 1:
 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
 kcsan_setup_watchpoint+0x404/0x410 kernel/kcsan/core.c:705
 unix_dgram_sendmsg+0xa40/0x1000 net/unix/af_unix.c:2286
 sock_sendmsg_nosec net/socket.c:727 [inline]
 __sock_sendmsg+0x145/0x170 net/socket.c:742
 sock_write_iter+0x1d2/0x210 net/socket.c:1195
 new_sync_write fs/read_write.c:593 [inline]
 vfs_write+0x5a6/0x9f0 fs/read_write.c:686
 ksys_write+0xdc/0x1a0 fs/read_write.c:738
 __do_sys_write fs/read_write.c:749 [inline]
 __se_sys_write fs/read_write.c:746 [inline]
 __x64_sys_write+0x40/0x50 fs/read_write.c:746
 x64_sys_call+0x2847/0x3000 arch/x86/include/generated/asm/syscalls_64.h:2
 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 0xffff888103450b88 of 8 bytes by task 25687 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/0xb60 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:1793
 io_issue_sqe+0x56/0xa70 io_uring/io_uring.c:1816
 io_queue_sqe io_uring/io_uring.c:2043 [inline]
 io_req_task_submit+0x46/0xa0 io_uring/io_uring.c:1435
 io_poll_task_func+0x5c4/0x770 io_uring/poll.c:-1
 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: 0x00000000000141c0 -> 0x00000000000142c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 25687 Comm: syz.0.5462 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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