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BUG: KCSAN: data-race in do_nanosleep / prepare_signal

write to 0xffff8880a05980a4 of 4 bytes by task 28052 on cpu 0:
 freezer_do_not_count include/linux/freezer.h:109 [inline]
 freezable_schedule include/linux/freezer.h:171 [inline]
 do_nanosleep+0xff/0x3a0 kernel/time/hrtimer.c:1879
 hrtimer_nanosleep kernel/time/hrtimer.c:1932 [inline]
 __do_sys_nanosleep kernel/time/hrtimer.c:1966 [inline]
 __se_sys_nanosleep+0x20b/0x2a0 kernel/time/hrtimer.c:1953
 __x64_sys_nanosleep+0x2d/0x40 kernel/time/hrtimer.c:1953
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880a05980a4 of 4 bytes by interrupt on cpu 1:
 sig_task_ignored kernel/signal.c:94 [inline]
 sig_ignored kernel/signal.c:119 [inline]
 prepare_signal+0x88d/0xdb0 kernel/signal.c:961
 send_sigqueue+0xea/0x450 kernel/signal.c:1860
 posix_timer_event kernel/time/posix-timers.c:354 [inline]
 posix_timer_fn+0xe8/0x210 kernel/time/posix-timers.c:380
 __run_hrtimer+0x154/0x4b0 kernel/time/hrtimer.c:1520
 __hrtimer_run_queues kernel/time/hrtimer.c:1584 [inline]
 hrtimer_interrupt+0x37c/0xa40 kernel/time/hrtimer.c:1646
 local_apic_timer_interrupt arch/x86/kernel/apic/apic.c:1080 [inline]
 __sysvec_apic_timer_interrupt+0xa3/0x280 arch/x86/kernel/apic/apic.c:1097
 asm_call_on_stack+0xf/0x20 arch/x86/entry/entry_64.S:711
 __run_on_irqstack arch/x86/include/asm/irq_stack.h:22 [inline]
 run_on_irqstack_cond arch/x86/include/asm/irq_stack.h:48 [inline]
 sysvec_apic_timer_interrupt+0x80/0xd0 arch/x86/kernel/apic/apic.c:1091
 asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:585
 __sanitizer_cov_trace_const_cmp4+0x4/0xa0 kernel/kcov.c:285
 wait_task_stopped kernel/exit.c:1148 [inline]
 wait_consider_task+0x2c1/0x18c0 kernel/exit.c:1352
 do_wait_thread kernel/exit.c:1378 [inline]
 do_wait+0x1b1/0x4e0 kernel/exit.c:1449
 kernel_wait4+0x13c/0x1a0 kernel/exit.c:1621
 __do_sys_wait4 kernel/exit.c:1633 [inline]
 __se_sys_wait4 kernel/exit.c:1629 [inline]
 __x64_sys_wait4+0x7a/0x100 kernel/exit.c:1629
 do_syscall_64+0x51/0xb0 arch/x86/entry/common.c:384
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 9103 Comm: syz-executor.4 Not tainted 5.8.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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