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BUG: KCSAN: data-race in p9_poll_workfn / p9_write_work

write to 0xffff888119847c9c of 4 bytes by task 1051 on cpu 1:
 p9_write_work+0x414/0x720 net/9p/trans_fd.c:500
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888119847c9c of 4 bytes by task 2968 on cpu 0:
 p9_poll_mux net/9p/trans_fd.c:648 [inline]
 p9_poll_workfn+0x1cf/0x3e0 net/9p/trans_fd.c:1172
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x00000015 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2968 Comm: kworker/0:2 Not tainted 6.15.0-rc6-syzkaller #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: events p9_poll_workfn
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