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BUG: KCSAN: data-race in del_timer / detach_if_pending

write to 0xffff888056ac4150 of 8 bytes by task 7971 on cpu 0:
 __hlist_del include/linux/list.h:764 [inline]
 detach_timer kernel/time/timer.c:815 [inline]
 detach_if_pending+0xcd/0x290 kernel/time/timer.c:832
 del_timer kernel/time/timer.c:1200 [inline]
 del_timer+0x67/0xb0 kernel/time/timer.c:1190
 try_to_grab_pending+0x22d/0x3e0 kernel/workqueue.c:1246
 __cancel_work kernel/workqueue.c:3216 [inline]
 cancel_delayed_work+0x45/0x1c0 kernel/workqueue.c:3245
 __rpc_disable_timer net/sunrpc/sched.c:92 [inline]
 __rpc_remove_wait_queue net/sunrpc/sched.c:242 [inline]
 __rpc_do_wake_up_task_on_wq net/sunrpc/sched.c:517 [inline]
 rpc_wake_up_task_on_wq_queue_action_locked net/sunrpc/sched.c:536 [inline]
 rpc_wake_up_task_on_wq_queue_action_locked+0x614/0x6d0 net/sunrpc/sched.c:528
 rpc_wake_up_task_queue_locked net/sunrpc/sched.c:550 [inline]
 rpc_wake_up_status+0xca/0x120 net/sunrpc/sched.c:743
 xprt_wake_pending_tasks+0x5f/0x70 net/sunrpc/xprt.c:532
 xs_tcp_setup_socket+0x21e/0x710 net/sunrpc/xprtsock.c:2415
 process_one_work+0x3d4/0x890 kernel/workqueue.c:2264
 worker_thread+0xa0/0x800 kernel/workqueue.c:2410
 kthread+0x1d4/0x200 drivers/block/aoe/aoecmd.c:1253
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:352

read to 0xffff888056ac4150 of 8 bytes by task 18714 on cpu 1:
 del_timer+0x3b/0xb0 kernel/time/timer.c:1198
 try_to_grab_pending+0x22d/0x3e0 kernel/workqueue.c:1246
 __cancel_work kernel/workqueue.c:3216 [inline]
 cancel_delayed_work+0x45/0x1c0 kernel/workqueue.c:3245
 __rpc_disable_timer net/sunrpc/sched.c:92 [inline]
 __rpc_remove_wait_queue net/sunrpc/sched.c:242 [inline]
 __rpc_do_wake_up_task_on_wq net/sunrpc/sched.c:517 [inline]
 rpc_wake_up_task_on_wq_queue_action_locked net/sunrpc/sched.c:536 [inline]
 rpc_wake_up_task_on_wq_queue_action_locked+0x614/0x6d0 net/sunrpc/sched.c:528
 rpc_wake_up_task_queue_locked net/sunrpc/sched.c:550 [inline]
 rpc_wake_up_queued_task net/sunrpc/sched.c:562 [inline]
 rpc_wake_up_queued_task+0x81/0xa0 net/sunrpc/sched.c:557
 rpc_exit net/sunrpc/sched.c:860 [inline]
 __rpc_execute+0x236/0x640 net/sunrpc/sched.c:955
 rpc_execute+0x1b5/0x1c0 net/sunrpc/sched.c:982
 rpc_run_task+0x379/0x440 net/sunrpc/clnt.c:1136
 rpc_call_sync+0xa7/0x130 net/sunrpc/clnt.c:1165
 rpc_ping net/sunrpc/clnt.c:2719 [inline]
 rpc_create_xprt+0x376/0x3d0 net/sunrpc/clnt.c:482
 rpc_create+0x2e4/0x4e0 net/sunrpc/clnt.c:598
 nfs_create_rpc_client+0x3d7/0x450 fs/nfs/client.c:532
 nfs_init_client fs/nfs/client.c:647 [inline]
 nfs_init_client+0x69/0xc0 fs/nfs/client.c:634
 nfs_get_client+0x91d/0xa00 fs/nfs/client.c:428
 nfs_init_server+0x1d8/0x7a0 fs/nfs/client.c:686
 nfs_create_server+0xcc/0x3d0 fs/nfs/client.c:973
 nfs_try_mount+0xa0/0x560 fs/nfs/super.c:1904
 nfs_fs_mount+0x7e7/0x15c0 fs/nfs/super.c:2766
 legacy_get_tree+0x7e/0xf0 fs/fs_context.c:647
 vfs_get_tree+0x56/0x1a0 fs/super.c:1545
 do_new_mount fs/namespace.c:2822 [inline]
 do_mount+0x1004/0x14f0 fs/namespace.c:3142
 ksys_mount+0xe8/0x160 fs/namespace.c:3351
 __do_sys_mount fs/namespace.c:3365 [inline]
 __se_sys_mount fs/namespace.c:3362 [inline]
 __x64_sys_mount+0x70/0x90 fs/namespace.c:3362
 do_syscall_64+0xcc/0x3a0 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 18714 Comm: syz-executor.5 Not tainted 5.5.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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