call_once is using relaxed atomic load to perform double-checked locking, which contains a data race. The fast-path load has to be an acquire atomic load.

Differential Revision: https://reviews.llvm.org/D24028

llvm-svn: 280621

This patch extracts out all the pthread dependencies of libcxx into the
new header __threading_support. The motivation is to make it easy to
re-target libcxx into platforms that do not support pthread.

Original patch from Fulvio Esposito (fulvio.esposito@outlook.com) - D11781

Applied with tweaks - D19412

Change-Id: I301111f0075de93dd8129416e06babc195aa936b
llvm-svn: 268734

llvm-svn: 245354

Summary:
In some places in libc++ we need to use the `__atomic_*` builtins. This patch adds a header that provides access to those builtins in a uniform way from within the dylib source.

If the compiler building the dylib does not support these builtins then a warning is issued.

Only relaxed loads are needed within the headers. A singe function to do these relaxed loads has been added to `<memory>`.

This patch applies the new atomic builtins to `__shared_count` and `call_once`.

Reviewers: mclow.lists

Subscribers: majnemer, jroelofs, cfe-commits

Differential Revision: http://reviews.llvm.org/D10406

llvm-svn: 241532

If you're crazy enough to want this sort of thing, then add
-D_LIBCPP_HAS_NO_THREADS to your CXXFLAGS and
--param=additiona_features=libcpp-has-no-threads to your lit commnad line.

http://reviews.llvm.org/D3969

llvm-svn: 217271

llvm-svn: 191148

llvm-svn: 160604

llvm-svn: 145624

llvm-svn: 119395

llvm-svn: 111751

llvm-svn: 110828

llvm-svn: 105393

patch by Jeffrey Yasskin for porting to Ubuntu Hardy.  Everything was accepted except there were some bug fixes needed in <locale> for the __nolocale_* series.  For the apple branch I ended up using templates instead of the var_args solution because it seemed both safer and more efficient.

llvm-svn: 104516

llvm-svn: 103516

llvm-svn: 103490