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, 46 insertions, 0 deletions

diff --git a/rts/StablePtr.h b/rts/StablePtr.h
new file mode 100644
index 0000000000..3fb305b47b
--- /dev/null
+++ b/rts/StablePtr.h
@@ -0,0 +1,46 @@
+/* -----------------------------------------------------------------------------
+ *
+ * (c) The GHC Team, 1998-2004
+ *
+ * Stable Pointers: A stable pointer is represented as an index into
+ * the stable pointer table.
+ *
+ * StgStablePtr used to be a synonym for StgWord, but stable pointers
+ * are guaranteed to be void* on the C-side, so we have to do some
+ * occasional casting. Size is not a matter, because StgWord is always
+ * the same size as a void*.
+ *
+ * ---------------------------------------------------------------------------*/
+
+#pragma once
+
+#include "sm/GC.h" // for evac_fn below
+
+#include "BeginPrivate.h"
+
+void    freeStablePtr         ( StgStablePtr sp );
+
+/* Use the "Unsafe" one after only when manually locking and
+   unlocking with stablePtrLock/stablePtrUnlock */
+void    freeStablePtrUnsafe   ( StgStablePtr sp );
+
+void    initStablePtrTable      ( void );
+void    exitStablePtrTable      ( void );
+
+/* Call given function on every stable ptr. markStablePtrTable depends
+ * on the function updating its pointers in case the object is
+ * moved.
+ */
+void    markStablePtrTable    ( evac_fn evac, void *user );
+
+void    threadStablePtrTable  ( evac_fn evac, void *user );
+
+void    stablePtrLock         ( void );
+void    stablePtrUnlock       ( void );
+
+#if defined(THREADED_RTS)
+// needed by Schedule.c:forkProcess()
+extern Mutex stable_ptr_mutex;
+#endif
+
+#include "EndPrivate.h"