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BUG: KCSAN: data-race in complete_signal / do_signal_stop

write to 0xffff88810ab3102c of 4 bytes by task 24535 on cpu 1:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 do_signal_stop+0x562/0x6d0 kernel/signal.c:2396
 get_signal+0xb18/0x1510 kernel/signal.c:2631
 arch_do_signal_or_restart+0x2a/0x270 arch/x86/kernel/signal.c:789
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x11a/0x1b0 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810ab3102c of 4 bytes by interrupt on cpu 0:
 wants_signal kernel/signal.c:978 [inline]
 complete_signal+0x189/0x600 kernel/signal.c:1014
 send_sigqueue+0x268/0x430 kernel/signal.c:1881
 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:1537
 __hrtimer_run_queues kernel/time/hrtimer.c:1601 [inline]
 hrtimer_interrupt+0x380/0xaf0 kernel/time/hrtimer.c:1663
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1089 [inline]
 __sysvec_apic_timer_interrupt+0x6f/0x200 arch/x86/kernel/apic/apic.c:1106
 sysvec_apic_timer_interrupt+0x69/0x80 arch/x86/kernel/apic/apic.c:1100
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632
 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:111 [inline]
 acpi_idle_do_entry drivers/acpi/processor_idle.c:517 [inline]
 acpi_idle_enter+0x25b/0x2e0 drivers/acpi/processor_idle.c:654
 cpuidle_enter_state+0x2b6/0x7c0 drivers/cpuidle/cpuidle.c:237
 cpuidle_enter+0x3c/0x60 drivers/cpuidle/cpuidle.c:351
 call_cpuidle kernel/sched/idle.c:158 [inline]
 cpuidle_idle_call kernel/sched/idle.c:239 [inline]
 do_idle+0x193/0x230 kernel/sched/idle.c:300
 cpu_startup_entry+0x15/0x20 kernel/sched/idle.c:397
 rest_init+0xd7/0xe0 init/main.c:721
 arch_call_rest_init+0xa/0xb
 start_kernel+0x5a1/0x626 init/main.c:1064
 secondary_startup_64_no_verify+0xb0/0xbb

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 0 Comm: swapper/0 Tainted: G        W         5.12.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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