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BUG: KCSAN: data-race in p9_conn_cancel / p9_poll_workfn

write to 0xffff88813c87ec28 of 4 bytes by task 10042 on cpu 1:
 p9_conn_cancel+0x89/0x400 net/9p/trans_fd.c:200
 p9_read_work+0x771/0x8d0 net/9p/trans_fd.c:407
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

read to 0xffff88813c87ec28 of 4 bytes by task 3171 on cpu 0:
 p9_poll_mux net/9p/trans_fd.c:626 [inline]
 p9_poll_workfn+0xc0/0x420 net/9p/trans_fd.c:1178
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:243

value changed: 0x00000000 -> 0xfffffffb

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 3171 Comm: kworker/0:4 Not tainted 6.9.0-rc1-syzkaller-00061-g8d025e2092e2 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
Workqueue: events p9_poll_workfn
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