ftrace: Synchronize the initialization of ftrace_opsgrafted

There's some internal state that ftrace_ops needs to have set, but since
it can be declared outside of the ftrace.c code, it calls
ftrace_ops_init() on the ops in every global function. The issue is that
if two tasks call it on the same ops at the same time it is possible to
have the initialization of one corrupt the initialization of the other
call.

Create a ops_mutex to use to synchronize every initialization of the
ftrace_ops. The mutex is taken within checking the ftrace_ops flag that
states it was initializied but the flag is checked again after the mutex
has been taken. Checking first outside the mutex allows it to shortcut
having to take the mutex. But then the check needs to be done again after
the mute is taken in case of races.

Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260902095501.6b59af20@gandalf.local.home
Fixes: f04f24fb7e48d ("ftrace, kprobes: Fix a deadlock on ftrace_regex_lock")
Reported-by: sashiko-bot@kernel.org
Close: https://lore.kernel.org/all/20260829025528.49A831F000E9@smtp.kernel.org/
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>

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__ */