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/tests/keep-tracking.c | 164 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 164 insertions(+) create mode 100644 tools/perf/tests/keep-tracking.c (limited to 'tools/perf/tests/keep-tracking.c') diff --git a/tools/perf/tests/keep-tracking.c b/tools/perf/tests/keep-tracking.c new file mode 100644 index 000000000..b760041be --- /dev/null +++ b/tools/perf/tests/keep-tracking.c @@ -0,0 +1,164 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include +#include +#include + +#include "debug.h" +#include "parse-events.h" +#include "evlist.h" +#include "evsel.h" +#include "record.h" +#include "thread_map.h" +#include "tests.h" +#include "util/mmap.h" + +#define CHECK__(x) { \ + while ((x) < 0) { \ + pr_debug(#x " failed!\n"); \ + goto out_err; \ + } \ +} + +#define CHECK_NOT_NULL__(x) { \ + while ((x) == NULL) { \ + pr_debug(#x " failed!\n"); \ + goto out_err; \ + } \ +} + +static int find_comm(struct evlist *evlist, const char *comm) +{ + union perf_event *event; + struct mmap *md; + int i, found; + + found = 0; + for (i = 0; i < evlist__core(evlist)->nr_mmaps; i++) { + md = &evlist__mmap(evlist)[i]; + if (perf_mmap__read_init(&md->core) < 0) + continue; + while ((event = perf_mmap__read_event(&md->core)) != NULL) { + if (event->header.type == PERF_RECORD_COMM && + (pid_t)event->comm.pid == getpid() && + (pid_t)event->comm.tid == getpid() && + strcmp(event->comm.comm, comm) == 0) + found += 1; + perf_mmap__consume(&md->core); + } + perf_mmap__read_done(&md->core); + } + return found; +} + +/** + * test__keep_tracking - test using a dummy software event to keep tracking. + * + * This function implements a test that checks that tracking events continue + * when an event is disabled but a dummy software event is not disabled. If the + * test passes %0 is returned, otherwise %-1 is returned. + */ +static int test__keep_tracking(struct test_suite *test __maybe_unused, int subtest __maybe_unused) +{ + struct record_opts opts = { + .mmap_pages = UINT_MAX, + .user_freq = UINT_MAX, + .user_interval = ULLONG_MAX, + .target = { + .uses_mmap = true, + }, + }; + struct perf_thread_map *threads = NULL; + struct perf_cpu_map *cpus = NULL; + struct evlist *evlist = NULL; + struct evsel *evsel = NULL; + int found, err = -1; + const char *comm; + + threads = thread_map__new_by_tid(getpid()); + CHECK_NOT_NULL__(threads); + + cpus = perf_cpu_map__new_online_cpus(); + CHECK_NOT_NULL__(cpus); + + evlist = evlist__new(); + CHECK_NOT_NULL__(evlist); + + perf_evlist__set_maps(evlist__core(evlist), cpus, threads); + + CHECK__(parse_event(evlist, "dummy:u")); + CHECK__(parse_event(evlist, "cpu-cycles:u")); + + evlist__config(evlist, &opts, NULL); + + evsel = evlist__first(evlist); + + evsel->core.attr.comm = 1; + evsel->core.attr.disabled = 1; + evsel->core.attr.enable_on_exec = 0; + + if (evlist__open(evlist) < 0) { + pr_debug("Unable to open dummy and cycles event\n"); + err = TEST_SKIP; + goto out_err; + } + + CHECK__(evlist__do_mmap(evlist, UINT_MAX)); + + /* + * First, test that a 'comm' event can be found when the event is + * enabled. + */ + + evlist__enable(evlist); + + comm = "Test COMM 1"; + CHECK__(prctl(PR_SET_NAME, (unsigned long)comm, 0, 0, 0)); + + evlist__disable(evlist); + + found = find_comm(evlist, comm); + if (found != 1) { + pr_debug("First time, failed to find tracking event.\n"); + goto out_err; + } + + /* + * Secondly, test that a 'comm' event can be found when the event is + * disabled with the dummy event still enabled. + */ + + evlist__enable(evlist); + + evsel = evlist__last(evlist); + + CHECK__(evsel__disable(evsel)); + + comm = "Test COMM 2"; + CHECK__(prctl(PR_SET_NAME, (unsigned long)comm, 0, 0, 0)); + + evlist__disable(evlist); + + found = find_comm(evlist, comm); + if (found != 1) { + pr_debug("Second time, failed to find tracking event.\n"); + goto out_err; + } + + err = 0; + +out_err: + if (evlist) { + evlist__disable(evlist); + evlist__put(evlist); + } + perf_cpu_map__put(cpus); + perf_thread_map__put(threads); + + return err; +} + +DEFINE_SUITE("Use a dummy software event to keep tracking", keep_tracking); -- cgit v1.3.1