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, 43 insertions, 0 deletions

diff --git a/tools/perf/util/pmus.h b/tools/perf/util/pmus.h
new file mode 100644
index 000000000..0d55edb3f
--- /dev/null
+++ b/tools/perf/util/pmus.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef __PMUS_H
+#define __PMUS_H
+
+#include <stdbool.h>
+#include <stddef.h>
+
+struct perf_event_attr;
+struct perf_pmu;
+struct print_callbacks;
+
+size_t pmu_name_len_no_suffix(const char *str);
+/* Exposed for testing only. */
+int pmu_name_cmp(const char *lhs_pmu_name, const char *rhs_pmu_name);
+
+void perf_pmus__destroy(void);
+
+struct perf_pmu *perf_pmus__find(const char *name);
+struct perf_pmu *perf_pmus__find_by_type(unsigned int type);
+struct perf_pmu *perf_pmus__find_by_attr(const struct perf_event_attr *attr);
+
+struct perf_pmu *perf_pmus__scan(struct perf_pmu *pmu);
+struct perf_pmu *perf_pmus__scan_core(struct perf_pmu *pmu);
+struct perf_pmu *perf_pmus__scan_for_event(struct perf_pmu *pmu, const char *event);
+struct perf_pmu *perf_pmus__scan_matching_wildcard(struct perf_pmu *pmu, const char *wildcard);
+struct perf_pmu *perf_pmus__scan_for_uncore_id(struct perf_pmu *pmu, const char *compat);
+
+const struct perf_pmu *perf_pmus__pmu_for_pmu_filter(const char *str);
+
+void perf_pmus__print_pmu_events(const struct print_callbacks *print_cb, void *print_state);
+void perf_pmus__print_raw_pmu_events(const struct print_callbacks *print_cb, void *print_state);
+bool perf_pmus__have_event(const char *pname, const char *name);
+int perf_pmus__num_core_pmus(void);
+bool perf_pmus__supports_extended_type(void);
+
+struct perf_pmu *perf_pmus__add_test_pmu(int test_sysfs_dirfd, const char *name);
+struct perf_pmu *perf_pmus__add_test_hwmon_pmu(const char *hwmon_dir,
+					       const char *sysfs_name,
+					       const char *name);
+struct perf_pmu *perf_pmus__fake_pmu(void);
+struct perf_pmu *perf_pmus__find_core_pmu(void);
+
+#endif /* __PMUS_H */