On Monday, 2 April 2007 22:51, Pavel Machek wrote:
> Hi!
>
> > > > +/* Per process freezer specific flags */
> > > > +#define PF_FE_SUSPEND 0x00008000 /* This thread should not be
> > > > frozen
> > > > + * for suspend
> > > > + */
> > > > +
> > > > +#define PF_FE_KPROBES 0x00000010 /* This thread should not be
> > > > frozen
> > > > + * for Kprobes
> > > > + */
> > >
> > > Just put the comment before the define for long comments?
> >
> > Agreed.
>
> (Actually it would be nice to say
>
> /* This thread should not be frozen for suspend, becuase it is needed
> for getting image saved to disk */
>
> > > > -#ifdef CONFIG_PM
> > > > +#if defined(CONFIG_PM) || defined(CONFIG_HOTPLUG_CPU) || \
> > > > + defined(CONFIG_KPROBES)
> > >
> > > Should we create CONFIG_FREEZER?
> >
> > Why do you think so? I think the freezer should be compiled automatically
> > if any of the above is set, which is what this directive really means.
>
> Kconfig can do that. ("select statement"). If we have one such ifdef,
> it is okay, but if it would be more of them.
>
> > > Hmmm, I do not really like softlockup watchdog running during suspend.
> > > Can we make this freezeable and make watchdog shut itself off while
> > > suspending?
> >
> > Generally, I agree, but this patch only replaces the existing instances
> > of PF_NOFREEZE with the new mechanism. The changes you're talking about
> > require a separate patch series (or at least one separate patch), I think,
> > and
> > they need not be so simple to make.
>
> Agreed about separate patch series.
>
> > > > - current->flags |= PF_NOFREEZE;
> > > > + freezer_exempt(FE_ALL);
> > > > pid = kernel_thread(do_linuxrc, "/linuxrc", SIGCHLD);
> > > > if (pid > 0) {
> > > > while (pid != sys_wait4(-1, NULL, 0, NULL))
> > >
> > > Does this mean we have userland /linuxrc running with PF_NOFREEZE?
> > > That would be very bad...
> >
> > No, actually it is _required_ for the userland resume to work. Well,
> > perhaps
> > I should place a comment in there so that I don't have to explain this again
> > and again. :-)
>
> Can you put big bold comment there?
>
> Why is it needed? Freezer never freezes _current_ task.
No, it doesn't, but this task spawns linuxrc and then calls sys_wait4() in a
loop.
Well, actually, I'll try to plant try_to_freeze() in this loop and see if that
works. If it doesn't, I'll add a comment.
> > > > @@ -104,7 +104,7 @@ static int __kprobes check_safety(void)
> > > > {
> > > > int ret = 0;
> > > > #if defined(CONFIG_PREEMPT) && defined(CONFIG_PM)
> > >
> > > Eh? Why does kprobes code depend on config_pm?
> >
> > Because it uses the freezer? ;-)
>
> That is no longer true after this patch... Ugly ifdef above makes sure
> freezer is there for kprobes. I'm trying to say that #if above is
> now broken. Actually it was probably always broken, but it just became
> more so.
Agreed.
Greetings,
Rafael
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