[grapefruit] SystemMonitor

[Peter Verswyvelen]

there is an atomicModifyIORef function. not sure if you can use that.
On Tue, Apr 7, 2009 at 4:09 PM, Wolfgang Jeltsch <g9ks157k at acme.softbase.org
> wrote:

> Am Montag, 6. April 2009 14:15 schrieb Peter Verswyvelen:
> > Can you tell a bit about the fix? Or is it clear from a diff on the
> > sources?
>
> I had accidently written readMVar instead of takeMVar in some module.
>
> I use MVars only because I fear that using IORefs might result in race
> conditions. I don’t know whether GHC automatically multithreads expression
> evaluation. If it does, using IORefs might be dangerous when they are
> accessed from within unsafePerformIO. Does anybody know more about the
> relationship between expression evaluation, multithreading and IORefs?
>
> Best wishes,
> Wolfgang
>
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