On Wed, Jun 02, 2021 at 10:06:58AM -0400, Mathieu Desnoyers wrote:
> ----- On Jun 2, 2021, at 9:12 AM, Peter Zijlstra pet...@infradead.org wrote:

> > @@ -134,14 +134,14 @@ struct task_group;
> >     do {                                                    \
> >             WARN_ON_ONCE(is_special_task_state(state_value));\
> >             current->task_state_change = _THIS_IP_;         \
> > -           current->state = (state_value);                 \
> > +           WRITE_ONCE(current->__state, (state_value));    \
> >     } while (0)
> 
> Why not introduce set_task_state(p) and get_task_state(p) rather than sprinkle
> READ_ONCE() and WRITE_ONCE() all over the kernel ?

set_task_state() is fundamentally unsound, there's very few sites that
_set_ state on anything other than current, and those sites are super
tricky, eg. ptrace.

Having get_task_state() would seem to suggest it's actually a sane thing
to do, it's not really. Inspecting remote state is full of races, and
some of that really wants cleaning up, but that's for another day.


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