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BUG: KCSAN: data-race in rcu_gp_fqs_check_wake / rcu_note_context_switch

write to 0xffffffff85a7d450 of 8 bytes by task 12555 on cpu 1:
 rcu_preempt_ctxt_queue kernel/rcu/tree_plugin.h:223 [inline]
 rcu_note_context_switch+0x6f6/0x760 kernel/rcu/tree_plugin.h:315
 __schedule+0xa4/0x640 kernel/sched/core.c:4007
 preempt_schedule_irq+0x57/0x90 kernel/sched/core.c:4319
 restore_regs_and_return_to_kernel+0x0/0x25
 find_watchpoint kernel/kcsan/core.c:67 [inline]
 check_access kernel/kcsan/core.c:388 [inline]
 __tsan_read8+0x54/0x1f0 kernel/kcsan/core.c:530
 mntput_no_expire+0x88/0x520 fs/namespace.c:1138
 mntput+0x5c/0x90 fs/namespace.c:1195
 path_put fs/namei.c:483 [inline]
 put_link fs/namei.c:877 [inline]
 step_into fs/namei.c:1762 [inline]
 walk_component+0x686/0xe70 fs/namei.c:1819
 lookup_last fs/namei.c:2263 [inline]
 path_lookupat.isra.0+0x13a/0x5a0 fs/namei.c:2308
 filename_lookup+0x145/0x2b0 fs/namei.c:2338
 user_path_at_empty+0x4c/0x70 fs/namei.c:2598
 user_path_at include/linux/namei.h:49 [inline]
 do_sys_truncate.part.0+0x57/0x100 fs/open.c:131
 do_sys_truncate fs/open.c:127 [inline]
 __do_sys_truncate fs/open.c:145 [inline]
 __se_sys_truncate fs/open.c:143 [inline]
 __x64_sys_truncate+0x53/0x80 fs/open.c:143
 do_syscall_64+0xcc/0x370 arch/x86/entry/common.c:290
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffffffff85a7d450 of 8 bytes by task 10 on cpu 0:
 rcu_gp_fqs_check_wake kernel/rcu/tree.c:1584 [inline]
 rcu_gp_fqs_check_wake+0x93/0xd0 kernel/rcu/tree.c:1574
 rcu_gp_fqs_loop+0x36c/0x580 kernel/rcu/tree.c:1639
 rcu_gp_kthread+0x143/0x230 kernel/rcu/tree.c:1799
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10 Comm: rcu_preempt Not tainted 5.4.0-rc6+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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