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Re: Optimization of conditional access to globals: thread-unsafe?


skaller writes:
 > 
 > On Fri, 2007-10-26 at 14:24 -0700, Ian Lance Taylor wrote:
 > 
 > > This is basically a public relations exercise.  I doubt this
 > > optimization is especially important, so I think it's OK to
 > > disable it to keep people happy.  Even though the optimization
 > > has been there since gcc 3.4 and nobody noticed.
 > 
 > Most people didn't have multi-core processors then..

It's partly that.  It's also that some people, particularly kernel
hackers, are super-paranoid about this sort of thing, and that's all
to the good.  The window of vulnerability introduced by this
"optimization" is extremely small -- but it is there.

As far as I can tell from reading the Linux kernel list, almost every
kernel programmer wants this transformation to be removed.  I suspect
that most pthreads programmers do too.  So yeah, it's mostly a public
relations exercise, but a worthwhile one.  I look forward to going to
the kernel list and telling them we've done what they wanted us to do.
They're an important part of our community.

Andrew.


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