Jan Kiszka wrote:
> Gilles Chanteperdrix wrote:
>> Jan Kiszka wrote:
>>> As we are already fighting hard to avoid new explicit mode-switch use
>>> cases, rather get rid of old ones, I thought it would be better to keep
>>> existing semantic across the fast mutex changes.
>>> Regarding those shared maps: they are per process, aren't they? But here
>>> we need per thread memory. I'm currently thinking of a memory piece that
>>> the caller of xeno_set_current provides (or some service that is called
>>> together with the latter one, or some extended services - to keep APIs
>>> clean). Then, on mode switches, the kernel will carefully
>>> (xn_copy_to_user) update it.
>> We can allocate a piece of memory on the shared heap, and attach it to a
>> thread using a pthread_key.
> What would be the advantage of using a heap chunk over doing xn_copy_*?
> I haven't looked into details yet but, in contrast to the mutex stuff, I
> don't expect that we will have to access that data from within critical
> regions.

Well, it is a more general solution, which should allow to access many
details in user-space. But I find it no real use right now.


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