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SubjectRE: [PATCH 2.5.52] Use __set_current_state() instead of current-> state = (take 1)
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> > - any setting before a return should be barriered unless we
> > return to a place[s] known to be harmless
>
> Not sure.

Well, I think it makes kind of sense. If we know we are
returning to some place where nothing bad could happen
with reordering ... well, so be it, don't use __set_...()

> > - any setting to TASK_RUNNING should be kind of safe
>
> Yes, I agree. It may race, but with what?

Hmmm ... I guess it could race, but it would not really
be that important [unless maybe certain constructs], as
the only setting it will go to would be [UN]INTERRUPTIBLE,
where it would be waken up afterwards, as it'd be out of the
rq, STOPPED, same thing, out of the rq, ZOMBIE or DEAD [gone].

I guess in this case, the only one I can come up with,
there would be an inconsistency between the actual state
of the task in task->state and the real one [or its position
in whatever rq or wq].

Could that have ugly consequences? I dunno ...

> > - current->state = TASK_UNINTERRUPTIBLE;
> > + __set_current_state(TASK_UNINTERRUPTIBLE);
> > spin_unlock_irq(&oldsig->siglock);
> >
> > Should be safe, as spin_unlock_irq() will do memory clobber
> > on sti() [undependant from UP/SMP].
>
> The memory clobber only acts as a compiler barrier and insures the
> compiler does not reorder the statements from the order in the C code.

while (1)
printk ("Inaky, remember, clobber is a hint to gcc\n");
And that would now really work when CONFIG_X86_OOSTORE=1 is required
[after all, it is a write, so it'd need the equivalent of a wmb() or
xchg()].
Okay, changing that one too, just in case.


Inaky Perez-Gonzalez -- Not speaking for Intel - opinions are my own [or my
fault]


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