On 22.08.25 16:42, Marek Marczykowski-Górecki wrote:
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.
I'm pretty sure the PV variant for suspending is just wrong: it is calling dpm_suspend_start() from do_suspend() without taking the required system_transition_mutex, resulting in the WARN() in pm_restrict_gfp_mask(). It might be as easy as just adding the mutex() call to do_suspend(), but I'm really not sure that will be a proper fix. Juergen
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