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, 356 insertions, 0 deletions

diff --git a/tools/perf/bench/futex-wake-parallel.c b/tools/perf/bench/futex-wake-parallel.c
new file mode 100644
index 000000000..6aede7c46
--- /dev/null
+++ b/tools/perf/bench/futex-wake-parallel.c
@@ -0,0 +1,356 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2015 Davidlohr Bueso.
+ *
+ * Block a bunch of threads and let parallel waker threads wakeup an
+ * equal amount of them. The program output reflects the avg latency
+ * for each individual thread to service its share of work. Ultimately
+ * it can be used to measure futex_wake() changes.
+ */
+#include "bench.h"
+#include <linux/compiler.h>
+#include "../util/debug.h"
+#include "../util/mutex.h"
+
+#ifndef HAVE_PTHREAD_BARRIER
+int bench_futex_wake_parallel(int argc __maybe_unused, const char **argv __maybe_unused)
+{
+	pr_err("%s: pthread_barrier_t unavailable, disabling this test...\n", __func__);
+	return 0;
+}
+#else /* HAVE_PTHREAD_BARRIER */
+/* For the CLR_() macros */
+#include <string.h>
+#include <pthread.h>
+
+#include <signal.h>
+#include "../util/stat.h"
+#include <subcmd/parse-options.h>
+#include <linux/kernel.h>
+#include <linux/time64.h>
+#include <errno.h>
+#include "futex.h"
+#include <perf/cpumap.h>
+
+#include <err.h>
+#include <stdlib.h>
+#include <sys/time.h>
+#include <sys/mman.h>
+
+struct thread_data {
+	pthread_t worker;
+	unsigned int nwoken;
+	struct timeval runtime;
+};
+
+static unsigned int nwakes = 1;
+
+/* all threads will block on the same futex -- hash bucket chaos ;) */
+static u_int32_t futex = 0;
+
+static pthread_t *blocked_worker;
+static bool done = false;
+static struct mutex thread_lock;
+static struct cond thread_parent, thread_worker;
+static pthread_barrier_t barrier;
+static struct stats waketime_stats, wakeup_stats;
+static unsigned int threads_starting;
+static int futex_flag = 0;
+
+static struct bench_futex_parameters params = {
+	.nbuckets = -1,
+};
+
+static const struct option options[] = {
+	OPT_INTEGER( 'b', "buckets", &params.nbuckets, "Specify amount of hash buckets"),
+	OPT_UINTEGER('t', "threads", &params.nthreads, "Specify amount of threads"),
+	OPT_UINTEGER('w', "nwakers", &params.nwakes, "Specify amount of waking threads"),
+	OPT_BOOLEAN( 's', "silent",  &params.silent, "Silent mode: do not display data/details"),
+	OPT_BOOLEAN( 'S', "shared",  &params.fshared, "Use shared futexes instead of private ones"),
+	OPT_BOOLEAN( 'm', "mlockall", &params.mlockall, "Lock all current and future memory"),
+
+	OPT_END()
+};
+
+static const char * const bench_futex_wake_parallel_usage[] = {
+	"perf bench futex wake-parallel <options>",
+	NULL
+};
+
+static void *waking_workerfn(void *arg)
+{
+	struct thread_data *waker = (struct thread_data *) arg;
+	struct timeval start, end;
+
+	pthread_barrier_wait(&barrier);
+
+	gettimeofday(&start, NULL);
+
+	waker->nwoken = futex_wake(&futex, nwakes, futex_flag);
+	if (waker->nwoken != nwakes)
+		warnx("couldn't wakeup all tasks (%d/%d)",
+		      waker->nwoken, nwakes);
+
+	gettimeofday(&end, NULL);
+	timersub(&end, &start, &waker->runtime);
+
+	pthread_exit(NULL);
+	return NULL;
+}
+
+static void wakeup_threads(struct thread_data *td)
+{
+	unsigned int i;
+	pthread_attr_t thread_attr;
+
+	pthread_attr_init(&thread_attr);
+	pthread_attr_setdetachstate(&thread_attr, PTHREAD_CREATE_JOINABLE);
+
+	pthread_barrier_init(&barrier, NULL, params.nwakes + 1);
+
+	/* create and block all threads */
+	for (i = 0; i < params.nwakes; i++) {
+		/*
+		 * Thread creation order will impact per-thread latency
+		 * as it will affect the order to acquire the hb spinlock.
+		 * For now let the scheduler decide.
+		 */
+		if (pthread_create(&td[i].worker, &thread_attr,
+				   waking_workerfn, (void *)&td[i]))
+			err(EXIT_FAILURE, "pthread_create");
+	}
+
+	pthread_barrier_wait(&barrier);
+
+	for (i = 0; i < params.nwakes; i++)
+		if (pthread_join(td[i].worker, NULL))
+			err(EXIT_FAILURE, "pthread_join");
+
+	pthread_barrier_destroy(&barrier);
+	pthread_attr_destroy(&thread_attr);
+}
+
+static void *blocked_workerfn(void *arg __maybe_unused)
+{
+	mutex_lock(&thread_lock);
+	threads_starting--;
+	if (!threads_starting)
+		cond_signal(&thread_parent);
+	cond_wait(&thread_worker, &thread_lock);
+	mutex_unlock(&thread_lock);
+
+	while (1) { /* handle spurious wakeups */
+		if (futex_wait(&futex, 0, NULL, futex_flag) != EINTR)
+			break;
+	}
+
+	pthread_exit(NULL);
+	return NULL;
+}
+
+static void block_threads(pthread_t *w, struct perf_cpu_map *cpu)
+{
+	cpu_set_t *cpuset;
+	unsigned int i;
+	int nrcpus = cpu__max_cpu().cpu;
+	size_t size;
+
+	threads_starting = params.nthreads;
+
+	cpuset = CPU_ALLOC(nrcpus);
+	BUG_ON(!cpuset);
+	size = CPU_ALLOC_SIZE(nrcpus);
+
+	/* create and block all threads */
+	for (i = 0; i < params.nthreads; i++) {
+		pthread_attr_t thread_attr;
+
+		pthread_attr_init(&thread_attr);
+		CPU_ZERO_S(size, cpuset);
+		CPU_SET_S(perf_cpu_map__cpu(cpu, i % perf_cpu_map__nr(cpu)).cpu, size, cpuset);
+
+		if (pthread_attr_setaffinity_np(&thread_attr, size, cpuset)) {
+			CPU_FREE(cpuset);
+			err(EXIT_FAILURE, "pthread_attr_setaffinity_np");
+		}
+
+		if (pthread_create(&w[i], &thread_attr, blocked_workerfn, NULL)) {
+			CPU_FREE(cpuset);
+			err(EXIT_FAILURE, "pthread_create");
+		}
+		pthread_attr_destroy(&thread_attr);
+	}
+	CPU_FREE(cpuset);
+}
+
+static void print_run(struct thread_data *waking_worker, unsigned int run_num)
+{
+	unsigned int i, wakeup_avg;
+	double waketime_avg, waketime_stddev;
+	struct stats __waketime_stats, __wakeup_stats;
+
+	init_stats(&__wakeup_stats);
+	init_stats(&__waketime_stats);
+
+	for (i = 0; i < params.nwakes; i++) {
+		update_stats(&__waketime_stats, waking_worker[i].runtime.tv_usec);
+		update_stats(&__wakeup_stats, waking_worker[i].nwoken);
+	}
+
+	waketime_avg = avg_stats(&__waketime_stats);
+	waketime_stddev = stddev_stats(&__waketime_stats);
+	wakeup_avg = avg_stats(&__wakeup_stats);
+
+	printf("[Run %d]: Avg per-thread latency (waking %d/%d threads) "
+	       "in %.4f ms (+-%.2f%%)\n", run_num + 1, wakeup_avg,
+	       params.nthreads, waketime_avg / USEC_PER_MSEC,
+	       rel_stddev_stats(waketime_stddev, waketime_avg));
+}
+
+static void print_summary(void)
+{
+	unsigned int wakeup_avg;
+	double waketime_avg, waketime_stddev;
+
+	waketime_avg = avg_stats(&waketime_stats);
+	waketime_stddev = stddev_stats(&waketime_stats);
+	wakeup_avg = avg_stats(&wakeup_stats);
+
+	printf("Avg per-thread latency (waking %d/%d threads) in %.4f ms (+-%.2f%%)\n",
+	       wakeup_avg,
+	       params.nthreads,
+	       waketime_avg / USEC_PER_MSEC,
+	       rel_stddev_stats(waketime_stddev, waketime_avg));
+	futex_print_nbuckets(&params);
+}
+
+
+static void do_run_stats(struct thread_data *waking_worker)
+{
+	unsigned int i;
+
+	for (i = 0; i < params.nwakes; i++) {
+		update_stats(&waketime_stats, waking_worker[i].runtime.tv_usec);
+		update_stats(&wakeup_stats, waking_worker[i].nwoken);
+	}
+
+}
+
+static void toggle_done(int sig __maybe_unused,
+			siginfo_t *info __maybe_unused,
+			void *uc __maybe_unused)
+{
+	done = true;
+}
+
+int bench_futex_wake_parallel(int argc, const char **argv)
+{
+	int ret = 0;
+	unsigned int i, j;
+	struct sigaction act;
+	struct thread_data *waking_worker;
+	struct perf_cpu_map *cpu;
+
+	argc = parse_options(argc, argv, options,
+			     bench_futex_wake_parallel_usage, 0);
+	if (argc) {
+		usage_with_options(bench_futex_wake_parallel_usage, options);
+		exit(EXIT_FAILURE);
+	}
+
+	memset(&act, 0, sizeof(act));
+	sigfillset(&act.sa_mask);
+	act.sa_sigaction = toggle_done;
+	sigaction(SIGINT, &act, NULL);
+
+	if (params.mlockall) {
+		if (mlockall(MCL_CURRENT | MCL_FUTURE))
+			err(EXIT_FAILURE, "mlockall");
+	}
+
+	cpu = perf_cpu_map__new_online_cpus();
+	if (!cpu)
+		err(EXIT_FAILURE, "calloc");
+
+	if (!params.nthreads)
+		params.nthreads = perf_cpu_map__nr(cpu);
+
+	/* some sanity checks */
+	if (params.nwakes > params.nthreads ||
+	    !params.nwakes)
+		params.nwakes = params.nthreads;
+
+	if (params.nthreads % params.nwakes)
+		errx(EXIT_FAILURE, "Must be perfectly divisible");
+	/*
+	 * Each thread will wakeup nwakes tasks in
+	 * a single futex_wait call.
+	 */
+	nwakes = params.nthreads/params.nwakes;
+
+	blocked_worker = calloc(params.nthreads, sizeof(*blocked_worker));
+	if (!blocked_worker)
+		err(EXIT_FAILURE, "calloc");
+
+	if (!params.fshared)
+		futex_flag = FUTEX_PRIVATE_FLAG;
+
+	futex_set_nbuckets_param(&params);
+
+	printf("Run summary [PID %d]: blocking on %d threads (at [%s] "
+	       "futex %p), %d threads waking up %d at a time.\n\n",
+	       getpid(), params.nthreads, params.fshared ? "shared":"private",
+	       &futex, params.nwakes, nwakes);
+
+	init_stats(&wakeup_stats);
+	init_stats(&waketime_stats);
+
+	mutex_init(&thread_lock);
+	cond_init(&thread_parent);
+	cond_init(&thread_worker);
+
+	for (j = 0; j < bench_repeat && !done; j++) {
+		waking_worker = calloc(params.nwakes, sizeof(*waking_worker));
+		if (!waking_worker)
+			err(EXIT_FAILURE, "calloc");
+
+		/* create, launch & block all threads */
+		block_threads(blocked_worker, cpu);
+
+		/* make sure all threads are already blocked */
+		mutex_lock(&thread_lock);
+		while (threads_starting)
+			cond_wait(&thread_parent, &thread_lock);
+		cond_broadcast(&thread_worker);
+		mutex_unlock(&thread_lock);
+
+		usleep(200000);
+
+		/* Ok, all threads are patiently blocked, start waking folks up */
+		wakeup_threads(waking_worker);
+
+		for (i = 0; i < params.nthreads; i++) {
+			ret = pthread_join(blocked_worker[i], NULL);
+			if (ret)
+				err(EXIT_FAILURE, "pthread_join");
+		}
+
+		do_run_stats(waking_worker);
+		if (!params.silent)
+			print_run(waking_worker, j);
+
+		free(waking_worker);
+	}
+
+	/* cleanup & report results */
+	cond_destroy(&thread_parent);
+	cond_destroy(&thread_worker);
+	mutex_destroy(&thread_lock);
+
+	print_summary();
+
+	free(blocked_worker);
+	perf_cpu_map__put(cpu);
+	return ret;
+}
+#endif /* HAVE_PTHREAD_BARRIER */