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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 10413 on cpu 0:
 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_unaligned_write8+0x54/0x1f0 kernel/kcsan/core.c:530
 xas_descend+0x7c/0x120 lib/xarray.c:205
 xas_load+0xd0/0x100 lib/xarray.c:239
 find_get_entry+0xdd/0x330 mm/filemap.c:1533
 pagecache_get_page+0x46/0x6f0 mm/filemap.c:1635
 find_get_page_flags include/linux/pagemap.h:266 [inline]
 __find_get_block_slow fs/buffer.c:207 [inline]
 __find_get_block fs/buffer.c:1296 [inline]
 __find_get_block+0x394/0x760 fs/buffer.c:1290
 sb_find_get_block include/linux/buffer_head.h:338 [inline]
 recently_deleted fs/ext4/ialloc.c:682 [inline]
 find_inode_bit.isra.0+0x161/0x300 fs/ext4/ialloc.c:722
 __ext4_new_inode+0xd10/0x2ec0 fs/ext4/ialloc.c:914
 ext4_create+0x152/0x370 fs/ext4/namei.c:2587
 lookup_open fs/namei.c:3224 [inline]
 do_last fs/namei.c:3314 [inline]
 path_openat+0x2b4b/0x36e0 fs/namei.c:3525
 do_filp_open+0x11e/0x1b0 fs/namei.c:3555
 do_sys_open+0x3b3/0x4f0 fs/open.c:1097
 __do_sys_open fs/open.c:1115 [inline]
 __se_sys_open fs/open.c:1110 [inline]
 __x64_sys_open+0x55/0x70 fs/open.c:1110
 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 1:
 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+0x39d/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: 1 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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