[compiler-rt] [asan] Switch initialization to "double-checked locking" (PR #74387)

[Vitaly Buka via llvm-commits]

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@@ -408,9 +406,8 @@ static void AsanInitInternal() {
   // Stop performing init at this point if we are being loaded via
   // dlopen() and the platform supports it.
   if (SANITIZER_SUPPORTS_INIT_FOR_DLOPEN && UNLIKELY(HandleDlopenInit())) {
-    SetAsanInitIsRunning(0);
     VReport(1, "AddressSanitizer init is being performed for dlopen().\n");
-    return;
+    return false;
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vitalybuka wrote:

To clarify

Before the patch
* `asan_inited = 0, asan_init_is_running = 0`: `__asan_handle_no_return` proceeds but likely going to crash, e.g. on [`llvm-project/compiler-rt/lib/asan/asan_poisoning.cpp:41`](https://github.com/llvm/llvm-project/blob/43455a2f0d3cdcd8dc46c4fbdebf4e655b26c2f2/compiler-rt/lib/asan/asan_poisoning.cpp#L41)
So we don't see this case in practice.

* `asan_inited = 0, asan_init_is_running = 1`: `__asan_handle_no_return` returns doing nothing 

* `asan_inited = 1, asan_init_is_running = 0`: `__asan_handle_no_return` works as expected

After the patch:
* `!AsanInited()`: `__asan_handle_no_return` return doing noting

* `AsanInited()`: `__asan_handle_no_return` works as expected

https://github.com/llvm/llvm-project/pull/74387