From 4fc21fffa908f83148120d24e888148014805a82 Mon Sep 17 00:00:00 2001
From: Florian Festi <ffesti@redhat.com>
Date: Thu, 10 Oct 2024 16:58:25 +0200
Subject: [PATCH] Turn FD_t->nrefs into atomic_int

Throughout the code base reference counting is done in a thread-unsave
way.

Turn nrefs into atomic_int so they are thread-save themselves. As the
nref can't change again after reaching zero this is thread-save even
as we look at the result an instruction later.

FD_t is special in that fdFree return the instance after free iff it
still has not reached a ref count of 0. Unfortunately code in
rpmShowProgress() relies on that.

This does not make the data structures thread save on its own. But it
gives a foundation on which data locking can be implemented.
---
 rpmio/rpmio.cc | 23 ++++++++++++-----------
 1 file changed, 12 insertions(+), 11 deletions(-)

diff --git a/rpmio/rpmio.cc b/rpmio/rpmio.cc
index 2131c03a11..77e6e7657e 100644
--- a/rpmio/rpmio.cc
+++ b/rpmio/rpmio.cc
@@ -12,6 +12,7 @@
 #include <dirent.h>
 #include <fcntl.h>
 #include <sys/resource.h>
+#include <atomic>
 
 #include <rpm/rpmlog.h>
 #include <rpm/rpmmacro.h>
@@ -46,7 +47,7 @@ typedef	struct {
  * The FD_t File Handle data structure.
  */
 struct FD_s {
-    int		nrefs;
+    std::atomic_int	nrefs;
     int		flags;
 #define	RPMIO_DEBUG_IO		0x40000000
     int		magic;
@@ -322,17 +323,17 @@ FD_t fdLink(FD_t fd)
 
 FD_t fdFree( FD_t fd)
 {
-    if (fd) {
-	if (--fd->nrefs > 0)
-	    return fd;
-	delete fd->stats;
-	if (fd->digests) {
-	    fd->digests = rpmDigestBundleFree(fd->digests);
-	}
-	delete fd->fps;
-	free(fd->descr);
-	delete fd;
+    if (fd == NULL || --fd->nrefs > 0)
+	return fd;
+
+    delete fd->stats;
+    if (fd->digests) {
+	fd->digests = rpmDigestBundleFree(fd->digests);
     }
+    delete fd->fps;
+    free(fd->descr);
+    delete fd;
+
     return NULL;
 }