From cd2c6aa32ae464da85676c820d42462fec25f1d5 Mon Sep 17 00:00:00 2001
From: Krasimir Angelov <kr.angelov@gmail.com>
Date: Wed, 29 Dec 2021 14:52:21 +0100
Subject: [PATCH] cleanup transient revisions only after a transaction is
 opened

---
 src/runtime/c/pgf/db.cxx  | 68 +++++++++++++++++++--------------------
 src/runtime/c/pgf/db.h    |  5 +--
 src/runtime/c/pgf/pgf.cxx |  2 ++
 3 files changed, 39 insertions(+), 36 deletions(-)

diff --git a/src/runtime/c/pgf/db.cxx b/src/runtime/c/pgf/db.cxx
index 62dff3dcc..140efc1af 100644
--- a/src/runtime/c/pgf/db.cxx
+++ b/src/runtime/c/pgf/db.cxx
@@ -502,7 +502,6 @@ struct PGF_INTERNAL_DECL malloc_state
 PGF_INTERNAL
 PgfDB::PgfDB(const char* filepath, int flags, int mode) {
     bool is_new = false;
-    bool is_first = false;
 
     fd = -1;
     ms = NULL;
@@ -655,34 +654,7 @@ PgfDB::PgfDB(const char* filepath, int flags, int mode) {
             throw pgf_error("Invalid file content");
         }
 
-        register_process(&is_first);
-
-        if (is_first) {
-            // We must make sure that left-over transient revisions are
-            // released. This may happen if a client process was killed
-            // or if the garbadge collector has not managed to run
-            // pgf_release_revision() before the process ended.
-
-            while (ms->transient_revisions != 0) {
-                pgf_free_revision(this, ms->transient_revisions.as_object());
-                ref<PgfPGF> pgf = ms->transient_revisions;
-                ref<PgfPGF> next = pgf->next;
-                PgfPGF::release(pgf);
-                PgfDB::free(pgf);
-                ms->transient_revisions = next;
-            }
-
-            while (ms->transient_concr_revisions != 0) {
-                ref<PgfConcr> concr = ms->transient_concr_revisions;
-                ref<PgfConcr> next = concr->next;
-                concr->ref_count -= concr->ref_count_ex;
-                if (!concr->ref_count) {
-                    PgfConcr::release(concr);
-                    PgfDB::free(concr);
-                }
-                ms->transient_concr_revisions = next;
-            }
-         }
+        register_process();
     }
 }
 
@@ -725,7 +697,7 @@ PgfDB::~PgfDB()
 }
 
 PGF_INTERNAL
-void PgfDB::register_process(bool *is_first)
+void PgfDB::register_process()
 {
     process_entry *pentry = &ms->p;
     object *plast = NULL;
@@ -768,10 +740,7 @@ void PgfDB::register_process(bool *is_first)
         }
     }
 
-    if (plast == NULL) {
-        *is_first = true;
-    } else {
-        *is_first = false;
+    if (plast != NULL) {
         *plast = malloc_internal(sizeof(process_entry));
         pentry = (process_entry*) ptr(ms,*plast);
         pentry->next = 0;
@@ -809,6 +778,37 @@ void PgfDB::unregister_process()
     }
 }
 
+void PgfDB::cleanup_revisions()
+{
+	if (ms->p.next == 0) {
+		// The first process that opens this file makes sure that
+		// left-over transient revisions are released.
+		// They may be left-over of a client process that was killed
+		// or if the garbadge collector has not managed to run
+		// pgf_release_revision() before the process ended.
+
+		while (ms->transient_revisions != 0) {
+			pgf_free_revision(this, ms->transient_revisions.as_object());
+			ref<PgfPGF> pgf = ms->transient_revisions;
+			ref<PgfPGF> next = pgf->next;
+			PgfPGF::release(pgf);
+			PgfDB::free(pgf);
+			ms->transient_revisions = next;
+		}
+
+		while (ms->transient_concr_revisions != 0) {
+			ref<PgfConcr> concr = ms->transient_concr_revisions;
+			ref<PgfConcr> next = concr->next;
+			concr->ref_count -= concr->ref_count_ex;
+			if (!concr->ref_count) {
+				PgfConcr::release(concr);
+				PgfDB::free(concr);
+			}
+			ms->transient_concr_revisions = next;
+		}
+	}
+}
+
 PGF_INTERNAL
 ref<PgfPGF> PgfDB::get_revision(PgfText *name)
 {
diff --git a/src/runtime/c/pgf/db.h b/src/runtime/c/pgf/db.h
index 16d702bbf..d1725588a 100644
--- a/src/runtime/c/pgf/db.h
+++ b/src/runtime/c/pgf/db.h
@@ -90,6 +90,8 @@ public:
         current_db->free_internal(o.as_object());
     }
 
+	PGF_INTERNAL_DECL void cleanup_revisions();
+
     static PGF_INTERNAL_DECL ref<PgfPGF> get_revision(PgfText *name);
     static PGF_INTERNAL_DECL void set_revision(ref<PgfPGF> pgf);
 
@@ -111,10 +113,9 @@ private:
     PGF_INTERNAL_DECL object malloc_internal(size_t bytes);
     PGF_INTERNAL_DECL void free_internal(object o);
 
-    PGF_INTERNAL_DECL void register_process(bool *is_first);
+    PGF_INTERNAL_DECL void register_process();
     PGF_INTERNAL_DECL void unregister_process();
 
-
     PGF_INTERNAL_DECL void lock(DB_scope_mode m);
     PGF_INTERNAL_DECL void unlock();
 
diff --git a/src/runtime/c/pgf/pgf.cxx b/src/runtime/c/pgf/pgf.cxx
index 10246eb32..182535a8f 100644
--- a/src/runtime/c/pgf/pgf.cxx
+++ b/src/runtime/c/pgf/pgf.cxx
@@ -144,6 +144,8 @@ PgfDB *pgf_read_ngf(const char *fpath,
         {
             DB_scope scope(db, WRITER_SCOPE);
 
+			db->cleanup_revisions();
+
             ref<PgfPGF> pgf = PgfDB::get_revision(master);
             Node<PgfPGF>::add_value_ref(pgf);
             *revision = pgf.as_object();