kern/sref: new module

This module provides multiprocessor scalable reference counters, based
on Refcache, as described in the RadixVM paper.

1 files changed, 48 insertions, 0 deletions

diff --git a/kern/sref_i.h b/kern/sref_i.h
new file mode 100644
index 00000000..158ad429
--- /dev/null
+++ b/kern/sref_i.h
@@ -0,0 +1,48 @@
+/*
+ * Copyright (c) 2014 Richard Braun.
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef _KERN_SREF_I_H
+#define _KERN_SREF_I_H
+
+#include <kern/spinlock.h>
+#include <kern/work.h>
+
+#define SREF_QUEUED 0x1
+#define SREF_DIRTY  0x2
+
+/*
+ * Scalable reference counter.
+ *
+ * It's tempting to merge the flags into the next member, but since they're
+ * not protected by the same lock, store them separately.
+ */
+struct sref_counter {
+    sref_noref_fn_t noref_fn;
+
+    union {
+        struct {
+            struct sref_counter *next;
+            struct spinlock lock;
+            int flags;
+            unsigned long value;
+        };
+
+        struct work work;
+    };
+};
+
+#endif /* _KERN_SREF_I_H */