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, 54 insertions, 0 deletions

diff --git a/tools/perf/util/iostat.c b/tools/perf/util/iostat.c
new file mode 100644
index 000000000..c9d5028a4
--- /dev/null
+++ b/tools/perf/util/iostat.c
@@ -0,0 +1,54 @@
+// SPDX-License-Identifier: GPL-2.0
+#include "util/iostat.h"
+#include "util/debug.h"
+
+enum iostat_mode_t iostat_mode = IOSTAT_NONE;
+
+__weak int iostat_prepare(struct evlist **evlist __maybe_unused,
+			  struct perf_stat_config *config __maybe_unused)
+{
+	return -1;
+}
+
+__weak int iostat_parse(const struct option *opt __maybe_unused,
+			 const char *str __maybe_unused,
+			 int unset __maybe_unused)
+{
+	pr_err("iostat mode is not supported on current platform\n");
+	return -1;
+}
+
+__weak void iostat_list(struct evlist *evlist __maybe_unused,
+		       struct perf_stat_config *config __maybe_unused)
+{
+}
+
+__weak void iostat_release(struct evlist *evlist __maybe_unused)
+{
+}
+
+__weak void iostat_print_header_prefix(struct perf_stat_config *config __maybe_unused)
+{
+}
+
+__weak void iostat_print_metric(struct perf_stat_config *config __maybe_unused,
+				struct evsel *evsel __maybe_unused,
+				struct perf_stat_output_ctx *out __maybe_unused)
+{
+}
+
+__weak void iostat_prefix(struct evlist *evlist __maybe_unused,
+			  struct perf_stat_config *config __maybe_unused,
+			  char *prefix __maybe_unused,
+			  struct timespec *ts __maybe_unused)
+{
+}
+
+__weak void iostat_print_counters(struct evlist *evlist __maybe_unused,
+				  struct perf_stat_config *config __maybe_unused,
+				  struct timespec *ts __maybe_unused,
+				  char *prefix __maybe_unused,
+				  iostat_print_counter_t print_cnt_cb __maybe_unused,
+				  void *arg __maybe_unused)
+{
+}