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, 208 insertions, 0 deletions

diff --git a/tools/perf/util/lock-contention.h b/tools/perf/util/lock-contention.h
new file mode 100644
index 000000000..59c94190b
--- /dev/null
+++ b/tools/perf/util/lock-contention.h
@@ -0,0 +1,208 @@
+// SPDX-License-Identifier: GPL-2.0
+#ifndef PERF_LOCK_CONTENTION_H
+#define PERF_LOCK_CONTENTION_H
+
+#include <linux/list.h>
+#include <linux/rbtree.h>
+
+struct lock_filter {
+	int			nr_types;
+	int			nr_addrs;
+	int			nr_syms;
+	int			nr_cgrps;
+	int			nr_slabs;
+	unsigned int		*types;
+	unsigned long		*addrs;
+	char			**syms;
+	u64			*cgrps;
+	char			**slabs;
+};
+
+struct lock_delay {
+	char			*sym;
+	unsigned long		addr;
+	unsigned long		time;
+};
+
+struct lock_stat {
+	struct hlist_node	hash_entry;
+	struct rb_node		rb;		/* used for sorting */
+
+	u64			addr;		/* address of lockdep_map, used as ID */
+	char			*name;		/* for strcpy(), we cannot use const */
+	u64			*callstack;
+
+	unsigned int		nr_acquire;
+	unsigned int		nr_acquired;
+	unsigned int		nr_contended;
+	unsigned int		nr_release;
+
+	union {
+		unsigned int	nr_readlock;
+		unsigned int	flags;
+	};
+	unsigned int		nr_trylock;
+
+	/* these times are in nano sec. */
+	u64                     avg_wait_time;
+	u64			wait_time_total;
+	u64			wait_time_min;
+	u64			wait_time_max;
+
+	int			broken; /* flag of blacklist */
+	int			combined;
+};
+
+/*
+ * States of lock_seq_stat
+ *
+ * UNINITIALIZED is required for detecting first event of acquire.
+ * As the nature of lock events, there is no guarantee
+ * that the first event for the locks are acquire,
+ * it can be acquired, contended or release.
+ */
+#define SEQ_STATE_UNINITIALIZED      0	       /* initial state */
+#define SEQ_STATE_RELEASED	1
+#define SEQ_STATE_ACQUIRING	2
+#define SEQ_STATE_ACQUIRED	3
+#define SEQ_STATE_READ_ACQUIRED	4
+#define SEQ_STATE_CONTENDED	5
+
+/*
+ * MAX_LOCK_DEPTH
+ * Imported from include/linux/sched.h.
+ * Should this be synchronized?
+ */
+#define MAX_LOCK_DEPTH 48
+
+/* based on kernel/lockdep.c */
+#define LOCKHASH_BITS		12
+#define LOCKHASH_SIZE		(1UL << LOCKHASH_BITS)
+
+extern struct hlist_head *lockhash_table;
+
+/*
+ * struct lock_seq_stat:
+ * Place to put on state of one lock sequence
+ * 1) acquire -> acquired -> release
+ * 2) acquire -> contended -> acquired -> release
+ * 3) acquire (with read or try) -> release
+ * 4) Are there other patterns?
+ */
+struct lock_seq_stat {
+	struct list_head        list;
+	int			state;
+	u64			prev_event_time;
+	u64                     addr;
+
+	int                     read_count;
+};
+
+struct thread_stat {
+	struct rb_node		rb;
+
+	u32                     tid;
+	struct list_head        seq_list;
+};
+
+/*
+ * CONTENTION_STACK_DEPTH
+ * Number of stack trace entries to find callers
+ */
+#define CONTENTION_STACK_DEPTH  8
+
+/*
+ * CONTENTION_STACK_SKIP
+ * Number of stack trace entries to skip when finding callers.
+ * The first few entries belong to the locking implementation itself.
+ */
+#define CONTENTION_STACK_SKIP  4
+
+/*
+ * flags for lock:contention_begin
+ * Imported from include/trace/events/lock.h.
+ */
+#define LCB_F_SPIN	(1U << 0)
+#define LCB_F_READ	(1U << 1)
+#define LCB_F_WRITE	(1U << 2)
+#define LCB_F_RT	(1U << 3)
+#define LCB_F_PERCPU	(1U << 4)
+#define LCB_F_MUTEX	(1U << 5)
+
+struct evlist;
+struct machine;
+struct target;
+
+struct lock_contention_fails {
+	int task;
+	int stack;
+	int time;
+	int data;
+};
+
+struct lock_contention {
+	struct evlist *evlist;
+	struct target *target;
+	struct machine *machine;
+	struct hlist_head *result;
+	struct lock_filter *filters;
+	struct lock_delay *delays;
+	struct lock_contention_fails fails;
+	struct rb_root cgroups;
+	void *btf;
+	unsigned long map_nr_entries;
+	int max_stack;
+	int stack_skip;
+	int aggr_mode;
+	int owner;
+	int nr_filtered;
+	int nr_delays;
+	bool save_callstack;
+};
+
+struct option;
+int parse_call_stack(const struct option *opt, const char *str, int unset);
+bool needs_callstack(void);
+
+struct lock_stat *lock_stat_find(u64 addr);
+struct lock_stat *lock_stat_findnew(u64 addr, const char *name, int flags);
+
+bool match_callstack_filter(struct machine *machine, u64 *callstack, int max_stack_depth);
+
+
+#ifdef HAVE_BPF_SKEL
+int lock_contention_prepare(struct lock_contention *con);
+int lock_contention_start(void);
+int lock_contention_stop(void);
+int lock_contention_read(struct lock_contention *con);
+int lock_contention_finish(struct lock_contention *con);
+
+struct lock_stat *pop_owner_stack_trace(struct lock_contention *con);
+
+#else  /* !HAVE_BPF_SKEL */
+
+static inline int lock_contention_prepare(struct lock_contention *con __maybe_unused)
+{
+	return 0;
+}
+
+static inline int lock_contention_start(void) { return 0; }
+static inline int lock_contention_stop(void) { return 0; }
+static inline int lock_contention_finish(struct lock_contention *con __maybe_unused)
+{
+	return 0;
+}
+
+static inline int lock_contention_read(struct lock_contention *con __maybe_unused)
+{
+	return 0;
+}
+
+static inline struct lock_stat *pop_owner_stack_trace(struct lock_contention *con __maybe_unused)
+{
+	return NULL;
+}
+
+#endif  /* HAVE_BPF_SKEL */
+
+#endif  /* PERF_LOCK_CONTENTION_H */