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Re: [RFC] Should we declare errno with __thread on x86?
- From: Torvald Riegel <triegel at redhat dot com>
- To: Roland McGrath <roland at hack dot frob dot com>
- Cc: "H.J. Lu" <hjl dot tools at gmail dot com>, GNU C Library <libc-alpha at sourceware dot org>
- Date: Tue, 12 Apr 2016 20:30:35 +0200
- Subject: Re: [RFC] Should we declare errno with __thread on x86?
- Authentication-results: sourceware.org; auth=none
- References: <CAMe9rOrb8XPsTUKHMw7F-+iy7D=UH=5XP_K06wDAwka+RRDCgw at mail dot gmail dot com> <20160318231420 dot A1C7E2C3C66 at topped-with-meat dot com>
On Fri, 2016-03-18 at 16:14 -0700, Roland McGrath wrote:
> If real-world performance measurement does in fact justify it, we'll still
> need to be very circumspect about potential pitfalls (applications built
> with older compilers, etc). We'll need to put a lot of thought into it
> collectively to achieve confidence that it's a safe and sensible change for
> all our users.
I agree that this would need a thorough investigation and assessment of
risks of doing that. One risk I see is that it would likely make it
harder for us to support errno on threads of execution that are not OS
threads (eg, coroutines, or under work-stealing implementations). It's
just an integer, but generally I'd prefer not to expose more TLS than
necessary.