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Re: Adding a new thread model to GCC
- From: Torvald Riegel <triegel at redhat dot com>
- To: lh_mouse <lh_mouse at 126 dot com>
- Cc: gcc <gcc at gcc dot gnu dot org>, mingw-w64-public <mingw-w64-public at lists dot sourceforge dot net>
- Date: Wed, 13 Apr 2016 19:40:49 +0200
- Subject: Re: Adding a new thread model to GCC
- Authentication-results: sourceware.org; auth=none
- References: <2f3897eb dot bbc0e dot 1540ee9aa0b dot Coremail dot lh_mouse at 126 dot com>
On Wed, 2016-04-13 at 17:17 +0800, lh_mouse wrote:
> Hi all,
>
> The 'win32' thread model of gcc has been there since long long ago, being compatible with very old Windows versions, also having a number of drawbacks:
> 0) its implementation is very inefficient, and
> 1) its mutexes and condition variables require dynamic initialization and are unusable in C++11 as std::mutex requires a `constexpr` constructor, and
> 2) allocating a number of rarely used mutexes or condition variables would eventually make the system run out of kernel objects.
>
> As a solution for 1) and 2), Microsoft introduced keyed events, details of which can be found here:
> http://joeduffyblog.com/2006/11/28/windows-keyed-events-critical-sections-and-new-vista-synchronization-features/
Have you looked at WaitOnAddress and WakeByAddressSingle /
WakeByAddressAll too? AFAIK this is new in Windows 8, and seems similar
to futexes.
I think it might be better to get a std::synchronic (or similar)
implementation into GCC, and then use these to implement at least the
mutexes:
https://github.com/ogiroux/synchronic/blob/master/include/synchronic
One benefit would be that we then have one place where we have optimized
spinning/blocking in libstdc++ on Windows, and less platform-specific
code.