x86/amd_node: Fix PCI device reference counting in amd_smn_init()grafted

The local "root" pointer is a temporary variable used during the device
search. Therefore, refcount related to the search iterators should be cleaned
up after the search is complete.

Use the __free() cleanup macro to ensure the refcount is decremented when the
temporary pointer goes out of scope.

Additionally, increment the refcount when caching a root pointer. This ensures
the in-use refcount is separate from the temporary search refcounting.

Finally, drop the redundant "root = NULL" before the second search loop. The
pci_get_class() iterator always decrements the refcount of its "from"
argument, so the first loop can only fall through with "root" already NULL.

Fixes: 0a4b61d9c2e4 ("x86/amd_node: Fix AMD root device caching")
Closes: https://sashiko.dev/#/patchset/20260806160159.230453-1-jason.andryuk%40amd.com
Reported-by: Sashiko <sashiko-bot@kernel.org>
Assisted-by: LLM
Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Mario Limonciello (AMD) <superm1@kernel.org>
Cc: <stable@kernel.org>
Link: https://patch.msgid.link/20260903154325.74343-1-yazen.ghannam@amd.com

1 files changed, 58 insertions, 0 deletions

diff --git a/tools/perf/util/cgroup.h b/tools/perf/util/cgroup.h
new file mode 100644
index 000000000..7b1bda228
--- /dev/null
+++ b/tools/perf/util/cgroup.h
@@ -0,0 +1,58 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __CGROUP_H__
+#define __CGROUP_H__
+
+#include <linux/compiler.h>
+#include <linux/refcount.h>
+#include <linux/rbtree.h>
+#include "util/env.h"
+
+struct option;
+
+struct cgroup {
+	struct rb_node		node;
+	u64			id;
+	char			*name;
+	int			fd;
+	refcount_t		refcnt;
+};
+
+extern int nr_cgroups; /* number of explicit cgroups defined */
+extern bool cgrp_event_expanded;
+
+struct cgroup *cgroup__get(struct cgroup *cgroup);
+void cgroup__put(struct cgroup *cgroup);
+
+struct evlist;
+struct rblist;
+
+struct cgroup *cgroup__new(const char *name, bool do_open);
+struct cgroup *evlist__findnew_cgroup(struct evlist *evlist, const char *name);
+int evlist__expand_cgroup(struct evlist *evlist, const char *cgroups, bool open_cgroup);
+
+void evlist__set_default_cgroup(struct evlist *evlist, struct cgroup *cgroup);
+
+int parse_cgroups(const struct option *opt, const char *str, int unset);
+
+struct cgroup *cgroup__findnew(struct perf_env *env, uint64_t id,
+			       const char *path);
+struct cgroup *cgroup__find(struct perf_env *env, uint64_t id);
+struct cgroup *__cgroup__find(struct rb_root *root, uint64_t id);
+
+void perf_env__purge_cgroups(struct perf_env *env);
+
+#ifdef HAVE_FILE_HANDLE
+int read_cgroup_id(struct cgroup *cgrp);
+#else
+static inline int read_cgroup_id(struct cgroup *cgrp __maybe_unused)
+{
+	return -1;
+}
+#endif  /* HAVE_FILE_HANDLE */
+
+/* read all cgroups in the system and save them in the rbtree */
+void read_all_cgroups(struct rb_root *root);
+
+int cgroup_is_v2(const char *subsys);
+
+#endif /* __CGROUP_H__ */