Thread specific storage APIs

This patch introduces thread specific storage APIs
for tools which use `rb_internal_thread_event_hook` APIs.

* `rb_internal_thread_specific_key_create()` to create a tool specific
  thread local storage key and allocate the storage if not available.
* `rb_internal_thread_specific_set()` sets a data to thread and tool
  specific storage.
* `rb_internal_thread_specific_get()` gets a data in thread and tool
  specific storage.

Note that `rb_internal_thread_specific_get|set(thread_val, key)`
can be called without GVL and safe for async signal and safe for
multi-threading (native threads). So you can call it in any internal
thread event hooks. Further more you can call it from other native
threads. Of course `thread_val` should be living while accessing the
data from this function.

Note that you should not forget to clean up the set data.

1 files changed, 4 insertions, 0 deletions

diff --git a/vm.c b/vm.c
index 294ee389aa..d7ae74a968 100644
--- a/vm.c
+++ b/vm.c
@@ -3435,6 +3435,10 @@ thread_free(void *ptr)
         rb_bug("thread_free: keeping_mutexes must be NULL (%p:%p)", (void *)th, (void *)th->keeping_mutexes);
     }
 
+    if (th->specific_storage) {
+        ruby_xfree(th->specific_storage);
+    }
+
     rb_threadptr_root_fiber_release(th);
 
     if (th->vm && th->vm->ractor.main_thread == th) {