Re: domU suspend issue - freeze processes failed - Linux 6.16

["Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>]

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On Fri, Aug 22, 2025 at 04:39:33PM +0200, Marek Marczykowski-Górecki wrote:
> 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).

I forgot to include link for (a little) more details:
https://github.com/QubesOS/qubes-linux-kernel/pull/1157

Especially, there is another call trace with panic_on_warn enabled -
slightly different, but looks related.

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

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