bcraig added subscribers: rmaprath, bcraig.
bcraig added a comment.
You should look at __thread_specific_ptr in libcxx's <thread>. It does a lot
of these things in order to satisfy the requirements of
notify_all_at_thread_exit, set_value_at_thread_exit, and
make_ready_at_thread_exit.
@rmaprath has been doing some work to make the threading runtime library
swappable. I don't recall if his work extended to libcxxabi or not, but I'll
page him anyway.
This implementation of __cxa_thread_atexit doesn't interact nicely with shared
libraries. The following sequence of events causes unloaded code to get
invoked.
- Create thread 42
- Load library foo from thread 42
- Call a function with a thread_local object with a dtor.
- Unload library foo.
- Join thread 42
glibc does some extra work during __cxa_thread_atexit_impl to bump the
reference count of the shared library so that the user's "unload" doesn't
actually unload the library.
================
Comment at: src/cxa_thread_atexit.cpp:40
@@ +39,3 @@
+
+ ~DtorListHolder() {
+ run_dtors(get());
----------------
I think this is correct, but it needs some comments because it is not obvious
what (or why) this is implemented this way.
More specifically, document the cases where run_dtors is run because of
~DtorListHolder vs. the cases where run_dtors is run because of the callback
registered at pthread_key_create.
http://reviews.llvm.org/D21803
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