Re: [RFC PATCH v1 5/9] freezer: set default freeze priority for PF_SUSPEND_TASK processes

[Oleg Nesterov]

On 08/11, Zihuan Zhang wrote:
> 
> 在 2025/8/11 17:32, Oleg Nesterov 写道:
> >On 08/11, Zihuan Zhang wrote:
> >>在 2025/8/8 22:39, Oleg Nesterov 写道:
> >>>On 08/07, Zihuan Zhang wrote:
> >>>>--- a/kernel/power/process.c
> >>>>+++ b/kernel/power/process.c
> >>>>@@ -147,6 +147,7 @@ int freeze_processes(void)
> >>>>
> >>>>  	pm_wakeup_clear(0);
> >>>>  	pm_freezing = true;
> >>>>+	freeze_set_default_priority(current, FREEZE_PRIORITY_NEVER);
> >>>But why?
> >>>
> >>>Again, freeze_task() will return false anyway, this process is
> >>>PF_SUSPEND_TASK.
> >>I  think there is resaon put it here. For example, systemd-sleep is a
> >>user-space process that executes the suspend flow.
> >>
> >>  If we don’t set its freeze priority explicitly, our current code may end up
> >>with this user process being the last one that cannot freeze.
> >How so? sorry I don't follow.
>
> The problem is in this part:
>
> +            if (user_only && !(p->flags & PF_KTHREAD) && round <
> p->freeze_priority)
> +                continue;
>
> PF_SUSPEND_TASK is a user process, so it meets the “needs freezing”
> condition and todo gets incremented.
            ^^^^^^^^^^^^^^^^^^^^^^^^^

No.
	if (p == current || !freeze_task(p))
		continue;

	todo++;

Again, again, freeze_task(p) returns false.

> But it actually doesn’t need to freeze,
> so resulting in an infinite loop

I don't think so.

Oleg.