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BUG: KCSAN: data-race in complete_signal / do_signal_stop

write to 0xffff8880b898e0e4 of 4 bytes by task 10028 on cpu 1:
 freezer_count include/linux/freezer.h:121 [inline]
 freezable_schedule include/linux/freezer.h:173 [inline]
 do_signal_stop+0x1f0/0x4e0 kernel/signal.c:2390
 get_signal+0xa8f/0x1290 kernel/signal.c:2592
 do_signal+0x2b/0x670 arch/x86/kernel/signal.c:813
 exit_to_usermode_loop+0x24a/0x2c0 arch/x86/entry/common.c:160
 prepare_exit_to_usermode arch/x86/entry/common.c:195 [inline]
 syscall_return_slowpath+0x218/0x240 arch/x86/entry/common.c:278
 ret_from_fork+0x15/0x30 arch/x86/entry/entry_64.S:344

read to 0xffff8880b898e0e4 of 4 bytes by interrupt on cpu 0:
 wants_signal kernel/signal.c:972 [inline]
 complete_signal+0x1ba/0x5c0 kernel/signal.c:1008
 send_sigqueue+0x30c/0x500 kernel/signal.c:1879
 posix_timer_event kernel/time/posix-timers.c:353 [inline]
 posix_timer_fn+0x104/0x220 kernel/time/posix-timers.c:379
 __run_hrtimer kernel/time/hrtimer.c:1517 [inline]
 __hrtimer_run_queues+0x271/0x600 kernel/time/hrtimer.c:1579
 hrtimer_interrupt+0x226/0x490 kernel/time/hrtimer.c:1641
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1119 [inline]
 smp_apic_timer_interrupt+0xd8/0x270 arch/x86/kernel/apic/apic.c:1144
 apic_timer_interrupt+0xf/0x20 arch/x86/entry/entry_64.S:829
 native_safe_halt+0xe/0x10 arch/x86/include/asm/irqflags.h:60
 arch_safe_halt arch/x86/include/asm/paravirt.h:144 [inline]
 default_idle+0x21/0x170 arch/x86/kernel/process.c:695
 cpuidle_idle_call kernel/sched/idle.c:154 [inline]
 do_idle+0x1b7/0x290 kernel/sched/idle.c:269
 cpu_startup_entry+0x14/0x20 kernel/sched/idle.c:361
 rest_init+0xe4/0xeb init/main.c:632
 arch_call_rest_init+0x13/0x2b
 start_kernel+0xcc2/0xceb init/main.c:971
 secondary_startup_64+0xa4/0xb0 arch/x86/kernel/head_64.S:242

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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