[pypy-dev] Easy way to get access to cmpxchg?

[Timothy Baldridge]

What's the best way to tell rpython not to release the GIL during a given
block of code? I haven't been able to find any code that describes when the
GIL is acquired or when control could switch over to another thread. I'd
prefer to have my interpreter bytecodes be atomic from the point of view
from the program. If I had that, then I could easily build a psudo
compare_and_swap by doing this:

dont_release_gil()
if foo.bar == oldval:
  foo.bar = newval
enable_gil_releasing()

Thanks,

Timothy




On Sat, Feb 22, 2014 at 12:13 AM, Armin Rigo <arigo at tunes.org> wrote:

> Hi Timothy,
>
> On 22 February 2014 01:39, Timothy Baldridge <tbaldridge at gmail.com> wrote:
> > compare_and_swap(foo.bar, oldval, newval)
>
> At some point we added a way to do it (basically you can do it
> yourself, by writing a one-line function in C and calling it).  We no
> longer do that: it's too much of a mess if you start having
> non-GIL-protected code written in RPython.  Either you are extremely,
> extremely careful, or random things will explode.  What we do instead,
> e.g. in the stm branches, is to write more C code.  For the complete
> parts that really need to run without any GIL protection, C is better
> than RPython after all.
>
>
> A bientôt,
>
> Armin.
>



-- 
"One of the main causes of the fall of the Roman Empire was that-lacking
zero-they had no way to indicate successful termination of their C
programs."
(Robert Firth)
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