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BUG: KCSAN: data-race in do_notify_parent_cldstop / prepare_signal

write to 0xffff88810039b660 of 4 bytes by interrupt on cpu 1:
 prepare_signal+0x3e2/0x660 kernel/signal.c:967
 send_sigqueue+0x141/0x450 kernel/signal.c:1997
 posix_timer_event kernel/time/posix-timers.c:298 [inline]
 posix_timer_fn+0xdb/0x1e0 kernel/time/posix-timers.c:324
 __run_hrtimer kernel/time/hrtimer.c:1688 [inline]
 __hrtimer_run_queues+0x217/0x700 kernel/time/hrtimer.c:1752
 hrtimer_interrupt+0x20d/0x7b0 kernel/time/hrtimer.c:1814
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1098 [inline]
 __sysvec_apic_timer_interrupt+0x73/0x210 arch/x86/kernel/apic/apic.c:1115
 sysvec_apic_timer_interrupt+0x68/0x80 arch/x86/kernel/apic/apic.c:1109
 asm_sysvec_apic_timer_interrupt+0x1a/0x20 arch/x86/include/asm/idtentry.h:645
 native_safe_halt arch/x86/include/asm/irqflags.h:48 [inline]
 arch_safe_halt arch/x86/include/asm/irqflags.h:86 [inline]
 acpi_safe_halt+0x20/0x30 drivers/acpi/processor_idle.c:112
 acpi_idle_do_entry+0x19/0x30 drivers/acpi/processor_idle.c:573
 acpi_idle_enter+0x96/0xb0 drivers/acpi/processor_idle.c:707
 cpuidle_enter_state+0xc6/0x260 drivers/cpuidle/cpuidle.c:267
 cpuidle_enter+0x40/0x60 drivers/cpuidle/cpuidle.c:388
 call_cpuidle kernel/sched/idle.c:134 [inline]
 cpuidle_idle_call kernel/sched/idle.c:215 [inline]
 do_idle+0x194/0x230 kernel/sched/idle.c:282
 cpu_startup_entry+0x18/0x20 kernel/sched/idle.c:379
 start_secondary+0x82/0x90 arch/x86/kernel/smpboot.c:326
 secondary_startup_64_no_verify+0x168/0x16b

read to 0xffff88810039b660 of 4 bytes by task 6255 on cpu 0:
 do_notify_parent_cldstop+0x192/0x290 kernel/signal.c:2191
 do_signal_stop+0x4d7/0x570 kernel/signal.c:2489
 get_signal+0x745/0xff0 kernel/signal.c:2724
 arch_do_signal_or_restart+0x89/0x2a0 arch/x86/kernel/signal.c:308
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:286 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:297
 do_syscall_64+0x4d/0xc0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x00000014 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 6255 Comm: syz-executor.0 Not tainted 6.5.0-rc3-syzkaller-00016-g20ea1e7d13c1 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2023
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