Finish stable split

Long ago, the stable name table and stable pointer tables were one.
Now, they are separate, and have significantly different
implementations. I believe the time has come to finish the split
that began in #7674.

* Divide `rts/Stable` into `rts/StableName` and `rts/StablePtr`.

* Give each table its own mutex.

* Add FFI functions `hs_lock_stable_ptr_table` and
`hs_unlock_stable_ptr_table` and document them.
  These are intended to replace the previously undocumented
`hs_lock_stable_tables` and `hs_lock_stable_tables`,
  which are now documented as deprecated synonyms.

* Make `eqStableName#` use pointer equality instead of unnecessarily
comparing stable name table indices.

Reviewers: simonmar, bgamari, erikd

Reviewed By: bgamari

Subscribers: rwbarton, carter

GHC Trac Issues: #15555

Differential Revision: https://phabricator.haskell.org/D5084

1 files changed, 32 insertions, 0 deletions

diff --git a/includes/rts/StableName.h b/includes/rts/StableName.h
new file mode 100644
index 0000000000..d43ffcb2f6
--- /dev/null
+++ b/includes/rts/StableName.h
@@ -0,0 +1,32 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 1998-2009
+ *
+ * Stable Names
+ *
+ * Do not #include this file directly: #include "Rts.h" instead.
+ *
+ * To understand the structure of the RTS headers, see the wiki:
+ *   http://ghc.haskell.org/trac/ghc/wiki/Commentary/SourceTree/Includes
+ *
+ * ---------------------------------------------------------------------------*/
+
+#pragma once
+
+/* -----------------------------------------------------------------------------
+   PRIVATE from here.
+   -------------------------------------------------------------------------- */
+
+typedef struct {
+    StgPtr  addr;        // Haskell object when entry is in use, next free
+                         // entry (NULL when this is the last free entry)
+                         // otherwise. May be NULL temporarily during GC (when
+                         // pointee dies).
+
+    StgPtr  old;         // Old Haskell object, used during GC
+
+    StgClosure *sn_obj;  // The StableName object, or NULL when the entry is
+                         // free
+} snEntry;
+
+extern DLL_IMPORT_RTS snEntry *stable_name_table;