idl-loop: Move idl-loop into ovsdb-idl library.

idl-loop is needed in implementing other controller (i.e., vtep controller).
So, this commit moves the logic into ovsdb-idl library module.

Signed-off-by: Alex Wang <alexw@nicira.com>
Acked-by: Russell Bryant <rbryant@redhat.com>

2 files changed, 91 insertions, 0 deletions

diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
index 4ec703240..f0d5d9ca0 100644
--- a/lib/ovsdb-idl.c
+++ b/lib/ovsdb-idl.c
@@ -2632,3 +2632,75 @@ ovsdb_idl_parse_lock_notify(struct ovsdb_idl *idl,
         }
     }
 }
+
+void
+ovsdb_idl_loop_destroy(struct ovsdb_idl_loop *loop)
+{
+    if (loop) {
+        ovsdb_idl_destroy(loop->idl);
+    }
+}
+
+struct ovsdb_idl_txn *
+ovsdb_idl_loop_run(struct ovsdb_idl_loop *loop)
+{
+    ovsdb_idl_run(loop->idl);
+    loop->open_txn = (loop->committing_txn
+                      || ovsdb_idl_get_seqno(loop->idl) == loop->skip_seqno
+                      ? NULL
+                      : ovsdb_idl_txn_create(loop->idl));
+    return loop->open_txn;
+}
+
+void
+ovsdb_idl_loop_commit_and_wait(struct ovsdb_idl_loop *loop)
+{
+    if (loop->open_txn) {
+        loop->committing_txn = loop->open_txn;
+        loop->open_txn = NULL;
+
+        loop->precommit_seqno = ovsdb_idl_get_seqno(loop->idl);
+    }
+
+    struct ovsdb_idl_txn *txn = loop->committing_txn;
+    if (txn) {
+        enum ovsdb_idl_txn_status status = ovsdb_idl_txn_commit(txn);
+        if (status != TXN_INCOMPLETE) {
+            switch (status) {
+            case TXN_TRY_AGAIN:
+                /* We want to re-evaluate the database when it's changed from
+                 * the contents that it had when we started the commit.  (That
+                 * might have already happened.) */
+                loop->skip_seqno = loop->precommit_seqno;
+                if (ovsdb_idl_get_seqno(loop->idl) != loop->skip_seqno) {
+                    poll_immediate_wake();
+                }
+                break;
+
+            case TXN_SUCCESS:
+                /* If the database has already changed since we started the
+                 * commit, re-evaluate it immediately to avoid missing a change
+                 * for a while. */
+                if (ovsdb_idl_get_seqno(loop->idl) != loop->precommit_seqno) {
+                    poll_immediate_wake();
+                }
+                break;
+
+            case TXN_UNCHANGED:
+            case TXN_ABORTED:
+            case TXN_NOT_LOCKED:
+            case TXN_ERROR:
+                break;
+
+            case TXN_UNCOMMITTED:
+            case TXN_INCOMPLETE:
+                OVS_NOT_REACHED();
+
+            }
+            ovsdb_idl_txn_destroy(txn);
+            loop->committing_txn = NULL;
+        }
+    }
+
+    ovsdb_idl_wait(loop->idl);
+}
diff --git a/lib/ovsdb-idl.h b/lib/ovsdb-idl.h
index a49f84fb6..519412231 100644
--- a/lib/ovsdb-idl.h
+++ b/lib/ovsdb-idl.h
@@ -222,5 +222,24 @@ const struct ovsdb_idl_row *ovsdb_idl_txn_insert(
     const struct uuid *);
 
 struct ovsdb_idl *ovsdb_idl_txn_get_idl (struct ovsdb_idl_txn *);
+
+
+/* ovsdb_idl_loop provides an easy way to manage the transactions related
+ * to 'idl' and to cope with different status during transaction. */
+struct ovsdb_idl_loop {
+    struct ovsdb_idl *idl;
+    unsigned int skip_seqno;
+
+    struct ovsdb_idl_txn *committing_txn;
+    unsigned int precommit_seqno;
+
+    struct ovsdb_idl_txn *open_txn;
+};
+
+#define OVSDB_IDL_LOOP_INITIALIZER(IDL) { .idl = (IDL) }
+
+void ovsdb_idl_loop_destroy(struct ovsdb_idl_loop *);
+struct ovsdb_idl_txn *ovsdb_idl_loop_run(struct ovsdb_idl_loop *);
+void ovsdb_idl_loop_commit_and_wait(struct ovsdb_idl_loop *);
 
 #endif /* ovsdb-idl.h */