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BUG: KCSAN: data-race in expire_timers / try_to_del_timer_sync

write to 0xffff888237d376c8 of 8 bytes by interrupt on cpu 1:
 expire_timers+0x13d/0x250 kernel/time/timer.c:1463
 __run_timers+0x358/0x420 kernel/time/timer.c:1731
 run_timer_softirq+0x19/0x30 kernel/time/timer.c:1744
 __do_softirq+0x12c/0x26e kernel/softirq.c:558
 invoke_softirq kernel/softirq.c:432 [inline]
 __irq_exit_rcu+0x9a/0xb0 kernel/softirq.c:636
 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:638
 kcsan_setup_watchpoint+0x8b/0x3e0 kernel/kcsan/core.c:437
 copy_present_pte mm/memory.c:941 [inline]
 copy_pte_range+0x372/0x1470 mm/memory.c:1070
 copy_pmd_range mm/memory.c:1156 [inline]
 copy_pud_range mm/memory.c:1193 [inline]
 copy_p4d_range mm/memory.c:1217 [inline]
 copy_page_range+0x5da/0x8e0 mm/memory.c:1290
 dup_mmap+0x6ab/0x9c0 kernel/fork.c:598
 dup_mm+0x7c/0x210 kernel/fork.c:1379
 copy_mm kernel/fork.c:1431 [inline]
 copy_process+0x144f/0x2f70 kernel/fork.c:2119
 kernel_clone+0x14b/0x680 kernel/fork.c:2509
 __do_sys_clone kernel/fork.c:2626 [inline]
 __se_sys_clone kernel/fork.c:2610 [inline]
 __x64_sys_clone+0xb4/0xe0 kernel/fork.c:2610
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3d/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888237d376c8 of 8 bytes by task 11 on cpu 0:
 try_to_del_timer_sync+0xe3/0x290 kernel/time/timer.c:1231
 del_timer_sync kernel/time/timer.c:1378 [inline]
 schedule_timeout+0x108/0x240 kernel/time/timer.c:1879
 rcu_gp_fqs_loop kernel/rcu/tree.c:1996 [inline]
 rcu_gp_kthread+0xbf7/0xec0 kernel/rcu/tree.c:2169
 kthread+0x262/0x280 kernel/kthread.c:319
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:295

value changed: 0xffffc90000277e60 -> 0x0000000000000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11 Comm: rcu_sched Not tainted 5.14.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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