domU suspend issue - freeze processes failed - Linux 6.16

[Marek Marczykowski-Górecki <marmarek@xxxxxxxxxxxxxxxxxxxxxx>]

Hi,

When suspending domU I get the following issue:

    Freezing user space processes
    Freezing user space processes failed after 20.004 seconds (1 tasks refusing 
to freeze, wq_busy=0):
    task:xl              state:D stack:0     pid:466   tgid:466   ppid:1      
task_flags:0x400040 flags:0x00004006
    Call Trace:
     <TASK>
     __schedule+0x2f3/0x780
     schedule+0x27/0x80
     schedule_preempt_disabled+0x15/0x30
     __mutex_lock.constprop.0+0x49f/0x880
     unregister_xenbus_watch+0x216/0x230
     xenbus_write_watch+0xb9/0x220
     xenbus_file_write+0x131/0x1b0
     vfs_writev+0x26c/0x3d0
     ? do_writev+0xeb/0x110
     do_writev+0xeb/0x110
     do_syscall_64+0x84/0x2c0
     ? do_syscall_64+0x200/0x2c0
     ? generic_handle_irq+0x3f/0x60
     ? syscall_exit_work+0x108/0x140
     ? do_syscall_64+0x200/0x2c0
     ? __irq_exit_rcu+0x4c/0xe0
     entry_SYSCALL_64_after_hwframe+0x76/0x7e
    RIP: 0033:0x79b618138642
    RSP: 002b:00007fff9a192fc8 EFLAGS: 00000246 ORIG_RAX: 0000000000000014
    RAX: ffffffffffffffda RBX: 00000000024fd490 RCX: 000079b618138642
    RDX: 0000000000000003 RSI: 00007fff9a193120 RDI: 0000000000000014
    RBP: 00007fff9a193000 R08: 0000000000000000 R09: 0000000000000000
    R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000014
    R13: 00007fff9a193120 R14: 0000000000000003 R15: 0000000000000000
     </TASK>
    OOM killer enabled.
    Restarting tasks: Starting
    Restarting tasks: Done
    xen:manage: do_suspend: freeze processes failed -16

The process in question is `xl devd` daemon. It's a domU serving a
xenvif backend.

I noticed it on 6.16.1, but looking at earlier test logs I see it with
6.16-rc6 already (but interestingly, not 6.16-rc2 yet? feels weird given
seemingly no relevant changes between rc2 and rc6).

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab

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