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[libcxx] Two more threading dependencies

Authored by rmaprath on Jun 1 2016, 11:49 AM.



Bumped into these while working on the externally threaded variant. I think it makes most sense to group these two under the main threading API. This greatly simplifies the presentation of the externally threaded library variant as well.

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rmaprath updated this revision to Diff 59262.Jun 1 2016, 11:49 AM
rmaprath retitled this revision from to [libcxx] Two more threading dependencies.
rmaprath updated this object.
rmaprath added reviewers: EricWF, bcraig, mclow.lists.
rmaprath added a subscriber: cfe-commits.
bcraig added inline comments.Jun 1 2016, 11:56 AM

Why does this need to go in threading_support? Seems like this is mostly orthogonal to threading. libcxxabi seems like the better place to hold changes to terminate anyway.

rmaprath added inline comments.Jun 1 2016, 12:05 PM

I can clearly see the argument against it, was bit unsure of it myself.

Now, the reason I want this the most is because of the externally threaded API, where I need to do some cleanup of the storage allocated in __libcpp_thread_create(). See the change I had to do in D20328 (thread.cpp) where I introduced a __libcpp_thread_finalize() function just for the cleanup. Thought it would be much cleaner to bundle up the two together so that I can avoid an explicit #ifdef in the sources.

Is that enough of a justification? Or should I stick to the explicit #ifdef in the externally-threaded variant? I don't have a strong opinion here, either way is fine, this version is slightly more preferred.

bcraig added inline comments.Jun 2 2016, 2:22 PM

I guess this is fine. I just need to tell myself (and maybe it should be commented in the code?) that this isn't trying to replace std::terminate, it's trying to replace a chunk of the std::thread dtor. Having a custom hook for the std::thread dtor is reasonable, and this is a reasonable default implementation.

Note that you only get a chance to do things here when a user does naughty things and lets a joinable thread reach the std::thread dtor.

rmaprath updated this revision to Diff 59507.Jun 3 2016, 2:09 AM

Added a comment about ~std::thread() hook.

@EricWF: Gentle ping.

rmaprath abandoned this revision.Dec 30 2016, 3:41 AM

Most of this is no longer needed. I'll submit patches for the parts that are actually needed (e.g. nanosleep) later on. Thanks.