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BUG: KCSAN: data-race in do_notify_parent_cldstop / prepare_signal

write to 0xffff888136fa4960 of 4 bytes by interrupt on cpu 0:
 prepare_signal+0x522/0x7b0 kernel/signal.c:961
 send_sigqueue+0xea/0x430 kernel/signal.c:2009
 posix_timer_event kernel/time/posix-timers.c:354 [inline]
 posix_timer_fn+0xe8/0x210 kernel/time/posix-timers.c:380
 __run_hrtimer+0x163/0x460 kernel/time/hrtimer.c:1685
 __hrtimer_run_queues kernel/time/hrtimer.c:1749 [inline]
 hrtimer_interrupt+0x37e/0xac0 kernel/time/hrtimer.c:1811
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1086 [inline]
 __sysvec_apic_timer_interrupt+0xa3/0x240 arch/x86/kernel/apic/apic.c:1103
 sysvec_apic_timer_interrupt+0x88/0xb0 arch/x86/kernel/apic/apic.c:1097
 asm_sysvec_apic_timer_interrupt+0x12/0x20
 native_safe_halt arch/x86/include/asm/irqflags.h:51 [inline]
 arch_safe_halt arch/x86/include/asm/irqflags.h:89 [inline]
 acpi_safe_halt drivers/acpi/processor_idle.c:115 [inline]
 acpi_idle_do_entry drivers/acpi/processor_idle.c:556 [inline]
 acpi_idle_enter+0x282/0x300 drivers/acpi/processor_idle.c:692
 cpuidle_enter_state+0x2b4/0x7d0 drivers/cpuidle/cpuidle.c:237
 cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:351
 call_cpuidle kernel/sched/idle.c:155 [inline]
 cpuidle_idle_call kernel/sched/idle.c:236 [inline]
 do_idle+0x1b2/0x250 kernel/sched/idle.c:303
 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:400
 rest_init+0xfa/0x100 init/main.c:726
 arch_call_rest_init+0xa/0xb init/main.c:882
 start_kernel+0x5ea/0x66f init/main.c:1140
 secondary_startup_64_no_verify+0xc4/0xcb

read to 0xffff888136fa4960 of 4 bytes by task 18464 on cpu 1:
 do_notify_parent_cldstop+0x1c1/0x290
 do_signal_stop+0x634/0x800 kernel/signal.c:2504
 get_signal+0xc76/0x15b0 kernel/signal.c:2750
 arch_do_signal_or_restart+0x8c/0x2e0 arch/x86/kernel/signal.c:868
 handle_signal_work kernel/entry/common.c:149 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:187 [inline]
 exit_to_user_mode_prepare+0x10e/0x180 kernel/entry/common.c:222
 __syscall_exit_to_user_mode_work kernel/entry/common.c:304 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:315
 do_syscall_64+0x37/0x70 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000014 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18464 Comm: syz-executor.3 Not tainted 5.17.0-syzkaller-07593-g52deda9551a0-dirty #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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