auto merge of #9713 : sfackler/rust/dynamic_lib, r=alexcrichton

The root issue is that dlerror isn't reentrant or even thread safe.

The solution implemented here is to make a yielding spin lock over an
AtomicFlag. This is pretty hacky, but the best we can do at this point.
As far as I can tell, it isn't possible to create a global mutex without
having to initialize it in a single threaded context.

The Windows code isn't affected since errno is thread-local on Windows
and it's running in an atomically block to ensure there isn't a green
thread context switch.

Closes #8156

1 files changed, 12 insertions, 0 deletions

diff --git a/src/rt/rust_builtin.cpp b/src/rt/rust_builtin.cpp
index eeb0c95337a..34d1efd577d 100644
--- a/src/rt/rust_builtin.cpp
+++ b/src/rt/rust_builtin.cpp
@@ -609,6 +609,18 @@ rust_drop_linenoise_lock() {
     linenoise_lock.unlock();
 }
 
+static lock_and_signal dlerror_lock;
+
+extern "C" CDECL void
+rust_take_dlerror_lock() {
+    dlerror_lock.lock();
+}
+
+extern "C" CDECL void
+rust_drop_dlerror_lock() {
+    dlerror_lock.unlock();
+}
+
 extern "C" CDECL unsigned int
 rust_valgrind_stack_register(void *start, void *end) {
   return VALGRIND_STACK_REGISTER(start, end);