From 4617721c502b2ddaa4e324e86da4997edf738fa5 Mon Sep 17 00:00:00 2001 From: Steven Rostedt Date: Wed, 2 Sep 2026 09:55:01 -0400 Subject: ftrace: Synchronize the initialization of ftrace_ops 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 --- tools/perf/bench/pmu-scan.c | 187 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 187 insertions(+) create mode 100644 tools/perf/bench/pmu-scan.c (limited to 'tools/perf/bench/pmu-scan.c') diff --git a/tools/perf/bench/pmu-scan.c b/tools/perf/bench/pmu-scan.c new file mode 100644 index 000000000..14a464ad8 --- /dev/null +++ b/tools/perf/bench/pmu-scan.c @@ -0,0 +1,187 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Benchmark scanning sysfs files for PMU information. + * + * Copyright 2023 Google LLC. + */ +#include +#include +#include "bench.h" +#include "util/debug.h" +#include "util/pmu.h" +#include "util/pmus.h" +#include "util/stat.h" +#include +#include +#include +#include + +static unsigned int iterations = 100; + +struct pmu_scan_result { + char *name; + int nr_aliases; + int nr_formats; + int nr_caps; + bool is_core; +}; + +static const struct option options[] = { + OPT_UINTEGER('i', "iterations", &iterations, + "Number of iterations used to compute average"), + OPT_END() +}; + +static const char *const bench_usage[] = { + "perf bench internals pmu-scan ", + NULL +}; + +static int nr_pmus; +static struct pmu_scan_result *results; + +static int save_result(void) +{ + struct perf_pmu *pmu = NULL; + struct list_head *list; + struct pmu_scan_result *r; + + while ((pmu = perf_pmus__scan(pmu)) != NULL) { + r = realloc(results, (nr_pmus + 1) * sizeof(*r)); + if (r == NULL) + return -ENOMEM; + + results = r; + r = results + nr_pmus; + + r->name = strdup(pmu->name); + r->is_core = pmu->is_core; + r->nr_caps = pmu->nr_caps; + + r->nr_aliases = perf_pmu__num_events(pmu); + + r->nr_formats = 0; + list_for_each(list, &pmu->format) + r->nr_formats++; + + pr_debug("pmu[%d] name=%s, nr_caps=%d, nr_aliases=%d, nr_formats=%d\n", + nr_pmus, r->name, r->nr_caps, r->nr_aliases, r->nr_formats); + nr_pmus++; + } + + perf_pmus__destroy(); + return 0; +} + +static int check_result(bool core_only) +{ + struct pmu_scan_result *r; + struct perf_pmu *pmu; + struct list_head *list; + int nr; + + for (int i = 0; i < nr_pmus; i++) { + r = &results[i]; + if (core_only && !r->is_core) + continue; + + pmu = perf_pmus__find(r->name); + if (pmu == NULL) { + pr_err("Cannot find PMU %s\n", r->name); + return -1; + } + + if (pmu->nr_caps != (u32)r->nr_caps) { + pr_err("Unmatched number of event caps in %s: expect %d vs got %d\n", + pmu->name, r->nr_caps, pmu->nr_caps); + return -1; + } + + nr = perf_pmu__num_events(pmu); + if (nr != r->nr_aliases) { + pr_err("Unmatched number of event aliases in %s: expect %d vs got %d\n", + pmu->name, r->nr_aliases, nr); + return -1; + } + + nr = 0; + list_for_each(list, &pmu->format) + nr++; + if (nr != r->nr_formats) { + pr_err("Unmatched number of event formats in %s: expect %d vs got %d\n", + pmu->name, r->nr_formats, nr); + return -1; + } + } + return 0; +} + +static void delete_result(void) +{ + for (int i = 0; i < nr_pmus; i++) + free(results[i].name); + free(results); + + results = NULL; + nr_pmus = 0; +} + +static int run_pmu_scan(void) +{ + struct stats stats; + struct timeval start, end, diff; + double time_average, time_stddev; + u64 runtime_us; + int ret; + + init_stats(&stats); + pr_info("Computing performance of sysfs PMU event scan for %u times\n", + iterations); + + if (save_result() < 0) { + pr_err("Failed to initialize PMU scan result\n"); + return -1; + } + + for (int j = 0; j < 2; j++) { + bool core_only = (j == 0); + + for (unsigned int i = 0; i < iterations; i++) { + gettimeofday(&start, NULL); + if (core_only) + perf_pmus__scan_core(NULL); + else + perf_pmus__scan(NULL); + gettimeofday(&end, NULL); + timersub(&end, &start, &diff); + runtime_us = diff.tv_sec * USEC_PER_SEC + diff.tv_usec; + update_stats(&stats, runtime_us); + + ret = check_result(core_only); + perf_pmus__destroy(); + if (ret < 0) + break; + } + time_average = avg_stats(&stats); + time_stddev = stddev_stats(&stats); + pr_info(" Average%s PMU scanning took: %.3f usec (+- %.3f usec)\n", + core_only ? " core" : "", time_average, time_stddev); + } + delete_result(); + return 0; +} + +int bench_pmu_scan(int argc, const char **argv) +{ + int err = 0; + + argc = parse_options(argc, argv, options, bench_usage, 0); + if (argc) { + usage_with_options(bench_usage, options); + exit(EXIT_FAILURE); + } + + err = run_pmu_scan(); + + return err; +} -- cgit v1.3.1