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

[Zihuan Zhang]

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

> Oleg.