syzbot

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BUG: KCSAN: data-race in rtc_dev_poll / rtc_pie_update_irq

read-write to 0xffff888103ac1388 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
 __preempt_count_dec_and_test arch/x86/include/asm/preempt.h:95 [inline]
 __raw_spin_unlock_irq include/linux/spinlock_api_smp.h:188 [inline]
 _raw_spin_unlock_irq+0x12/0x30 kernel/locking/spinlock.c:202
 spin_unlock_irq include/linux/spinlock.h:401 [inline]
 swap_cluster_unlock_irq mm/swap.h:183 [inline]
 __remove_mapping+0x46d/0x4c0 mm/vmscan.c:764
 shrink_folio_list+0x1970/0x2820 mm/vmscan.c:1525
 reclaim_folio_list+0x9f/0x220 mm/vmscan.c:2205
 reclaim_pages+0x21e/0x280 mm/vmscan.c:2242
 madvise_cold_or_pageout_pte_range+0xd6a/0xdc0 mm/madvise.c:561
 walk_pmd_range mm/pagewalk.c:130 [inline]
 walk_pud_range mm/pagewalk.c:224 [inline]
 walk_p4d_range mm/pagewalk.c:262 [inline]
 walk_pgd_range+0xa4a/0x14d0 mm/pagewalk.c:303
 __walk_page_range+0xdd/0x340 mm/pagewalk.c:411
 walk_page_range_vma_unsafe+0x2cd/0x320 mm/pagewalk.c:715
 walk_page_range_vma+0x56/0x70 mm/pagewalk.c:725
 madvise_vma_behavior+0x1d11/0x20c0 mm/madvise.c:-1
 madvise_walk_vmas mm/madvise.c:1719 [inline]
 madvise_do_behavior+0x5de/0xa10 mm/madvise.c:1935
 do_madvise+0x10e/0x190 mm/madvise.c:2028
 __do_sys_madvise mm/madvise.c:2037 [inline]
 __se_sys_madvise mm/madvise.c:2035 [inline]
 __x64_sys_madvise+0x63/0x80 mm/madvise.c:2035
 x64_sys_call+0x1eff/0x3020 arch/x86/include/generated/asm/syscalls_64.h:29
 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

read to 0xffff888103ac1388 of 8 bytes by task 6978 on cpu 1:
 rtc_dev_poll+0x78/0xb0 drivers/rtc/dev.c:198
 vfs_poll include/linux/poll.h:82 [inline]
 io_file_supports_nowait io_uring/rw.c:47 [inline]
 __io_read+0x312/0xc50 io_uring/rw.c:937
 io_read+0x4a/0x190 io_uring/rw.c:1031
 __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_req_task_submit+0x46/0xa0 io_uring/io_uring.c:1044
 io_poll_task_func+0x5dd/0x7d0 io_uring/poll.c:-1
 io_handle_tw_list+0x121/0x230 io_uring/tw.c:72
 tctx_task_work_run+0x42/0x170 io_uring/tw.c:132
 tctx_task_work+0x3f/0x80 io_uring/tw.c:150
 task_work_run+0x130/0x1a0 kernel/task_work.c:233
 io_run_task_work+0x1fc/0x280 io_uring/tw.h:83
 io_cqring_wait+0x9d9/0xe10 io_uring/wait.c:271
 __do_sys_io_uring_enter io_uring/io_uring.c:2642 [inline]
 __se_sys_io_uring_enter+0x38e/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: 0x00000000000005c0 -> 0x00000000000006c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6978 Comm: syz.4.896 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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