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BUG: KCSAN: data-race in rcu_gp_fqs_check_wake / rcu_note_context_switch

write to 0xffffffff85a7f190 of 8 bytes by task 8102 on cpu 1:
 rcu_preempt_ctxt_queue kernel/rcu/tree_plugin.h:223 [inline]
 rcu_note_context_switch+0x72e/0x7a0 kernel/rcu/tree_plugin.h:316
 __schedule+0xa4/0x5d0 kernel/sched/core.c:3822
 preempt_schedule_irq+0x57/0x90 kernel/sched/core.c:4131
 restore_regs_and_return_to_kernel+0x0/0x25
 find_watchpoint kernel/kcsan/core.c:84 [inline]
 __kcsan_check_watchpoint+0x88/0x180 kernel/kcsan/core.c:322
 __tsan_write8+0x18/0x40 kernel/kcsan/kcsan.c:31
 radix_tree_load_root+0x98/0x100 lib/radix-tree.c:406
 __radix_tree_lookup+0x5e/0x1b0 lib/radix-tree.c:767
 radix_tree_lookup+0x2b/0x40 lib/radix-tree.c:828
 wb_find_current include/linux/backing-dev.h:276 [inline]
 wb_get_create_current include/linux/backing-dev.h:302 [inline]
 balance_dirty_pages_ratelimited+0x4af/0xb20 mm/page-writeback.c:1874
 generic_perform_write+0x22d/0x320 mm/filemap.c:3363
 __generic_file_write_iter+0x251/0x380 mm/filemap.c:3456
 ext4_file_write_iter+0x1fc/0xa40 fs/ext4/file.c:270
 call_write_iter include/linux/fs.h:1870 [inline]
 do_iter_readv_writev+0x487/0x5b0 fs/read_write.c:693

read to 0xffffffff85a7f190 of 8 bytes by task 10 on cpu 0:
 rcu_gp_fqs_check_wake kernel/rcu/tree.c:1556 [inline]
 rcu_gp_fqs_check_wake+0x93/0xd0 kernel/rcu/tree.c:1546
 rcu_gp_fqs_loop+0x36c/0x580 kernel/rcu/tree.c:1611
 rcu_gp_kthread+0x143/0x220 kernel/rcu/tree.c:1768
 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 5.3.0+ #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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