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, 152 insertions, 0 deletions

diff --git a/tools/perf/tests/sw-clock.c b/tools/perf/tests/sw-clock.c
new file mode 100644
index 000000000..d18185881
--- /dev/null
+++ b/tools/perf/tests/sw-clock.c
@@ -0,0 +1,152 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <errno.h>
+#include <inttypes.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <signal.h>
+#include <sys/mman.h>
+#include <linux/compiler.h>
+#include <linux/string.h>
+
+#include "tests.h"
+#include "util/debug.h"
+#include "util/evsel.h"
+#include "util/evlist.h"
+#include "util/cpumap.h"
+#include "util/mmap.h"
+#include "util/sample.h"
+#include "util/thread_map.h"
+#include <perf/evlist.h>
+#include <perf/mmap.h>
+
+#define NR_LOOPS  10000000
+
+/*
+ * This test will open software clock events (cpu-clock, task-clock)
+ * then check their frequency -> period conversion has no artifact of
+ * setting period to 1 forcefully.
+ */
+static int __test__sw_clock_freq(enum perf_sw_ids clock_id)
+{
+	int i, err = -1;
+	volatile int tmp __maybe_unused = 0;
+	u64 total_periods = 0;
+	int nr_samples = 0;
+	char sbuf[STRERR_BUFSIZE];
+	union perf_event *event;
+	struct evsel *evsel;
+	struct evlist *evlist;
+	struct perf_event_attr attr = {
+		.type = PERF_TYPE_SOFTWARE,
+		.config = clock_id,
+		.sample_type = PERF_SAMPLE_PERIOD,
+		.exclude_kernel = 1,
+		.disabled = 1,
+		.freq = 1,
+	};
+	struct perf_cpu_map *cpus = NULL;
+	struct perf_thread_map *threads = NULL;
+	struct mmap *md;
+
+	attr.sample_freq = 500;
+
+	evlist = evlist__new();
+	if (evlist == NULL) {
+		pr_debug("evlist__new\n");
+		return -1;
+	}
+
+	evsel = evsel__new(&attr);
+	if (evsel == NULL) {
+		pr_debug("evsel__new\n");
+		goto out_put_evlist;
+	}
+	evlist__add(evlist, evsel);
+
+	cpus = perf_cpu_map__new_any_cpu();
+	threads = thread_map__new_by_tid(getpid());
+	if (!cpus || !threads) {
+		err = -ENOMEM;
+		pr_debug("Not enough memory to create thread/cpu maps\n");
+		goto out_put_evlist;
+	}
+
+	perf_evlist__set_maps(evlist__core(evlist), cpus, threads);
+
+	if (evlist__open(evlist)) {
+		const char *knob = "/proc/sys/kernel/perf_event_max_sample_rate";
+
+		err = -errno;
+		pr_debug("Couldn't open evlist: %s\nHint: check %s, using %" PRIu64 " in this test.\n",
+			 str_error_r(errno, sbuf, sizeof(sbuf)),
+			 knob, (u64)attr.sample_freq);
+		goto out_put_evlist;
+	}
+
+	err = evlist__do_mmap(evlist, 128);
+	if (err < 0) {
+		pr_debug("failed to mmap event: %d (%s)\n", errno,
+			 str_error_r(errno, sbuf, sizeof(sbuf)));
+		goto out_put_evlist;
+	}
+
+	evlist__enable(evlist);
+
+	/* collect samples */
+	for (i = 0; i < NR_LOOPS; i++)
+		tmp++;
+
+	evlist__disable(evlist);
+
+	md = &evlist__mmap(evlist)[0];
+	if (perf_mmap__read_init(&md->core) < 0)
+		goto out_init;
+
+	while ((event = perf_mmap__read_event(&md->core)) != NULL) {
+		struct perf_sample sample;
+
+		perf_sample__init(&sample, /*all=*/false);
+		if (event->header.type != PERF_RECORD_SAMPLE)
+			goto next_event;
+
+		err = evlist__parse_sample(evlist, event, &sample);
+		if (err < 0) {
+			pr_debug("Error during parse sample\n");
+			perf_sample__exit(&sample);
+			goto out_put_evlist;
+		}
+
+		total_periods += sample.period;
+		nr_samples++;
+next_event:
+		perf_mmap__consume(&md->core);
+		perf_sample__exit(&sample);
+	}
+	perf_mmap__read_done(&md->core);
+
+out_init:
+	if ((u64) nr_samples == total_periods) {
+		pr_debug("All (%d) samples have period value of 1!\n",
+			 nr_samples);
+		err = -1;
+	}
+
+out_put_evlist:
+	perf_cpu_map__put(cpus);
+	perf_thread_map__put(threads);
+	evlist__put(evlist);
+	return err;
+}
+
+static int test__sw_clock_freq(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	int ret;
+
+	ret = __test__sw_clock_freq(PERF_COUNT_SW_CPU_CLOCK);
+	if (!ret)
+		ret = __test__sw_clock_freq(PERF_COUNT_SW_TASK_CLOCK);
+
+	return ret;
+}
+
+DEFINE_SUITE("Software clock events period values", sw_clock_freq);