perf test: Add test for events re-armed with PERF_EVENT_IOC_REFRESH

Open a sampling event with sample_period 1, re-arm it with
PERF_EVENT_IOC_REFRESH from its overflow signal handler, as
self-profilers such as async-profiler do, and check that each of 1000
events delivers a signal. One case uses a software event (page faults),
the other the syscalls:sys_enter_getppid tracepoint. The signal is a
real-time one, so overflows cannot be coalesced, and the page fault
buffer is marked MADV_NOHUGEPAGE so that each touched page faults once.

The tracepoint case fails since commit 18dbcbfabfffc4a5 ("perf: Fix the
POLL_HUP delivery breakage") only the first overflow is delivered. The
re-arming ioctl succeeds, but the event count stays at 1. It passes on
the parent commit. The software case passes on both.

The test was written with an AI coding assistant (Claude) from a
standalone reproducer; I reviewed it and ran it in QEMU on current
mainline, on that commit and on its parent.

Reviewed-by: Ian Rogers <irogers@google.com>
Signed-off-by: Francesco Nigro <nigro.fra@gmail.com>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

4 files changed, 165 insertions, 0 deletions

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index 395f2866094a..58858f3d2bf9 100644
--- a/tools/perf/tests/Build
+++ b/tools/perf/tests/Build
@@ -23,6 +23,7 @@ perf-test-y += hists_output.o
 perf-test-y += hists_cumulate.o
 perf-test-y += bp_signal.o
 perf-test-y += bp_signal_overflow.o
+perf-test-y += event_refresh.o
 perf-test-y += bp_account.o
 perf-test-y += wp.o
 perf-test-y += task-exit.o
diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
index 0751d974a39a..0b8897fd42ca 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -120,6 +120,7 @@ static struct test_suite *generic_tests[] = {
 	&suite__hists_link,
 	&suite__bp_signal,
 	&suite__bp_signal_overflow,
+	&suite__event_refresh,
 	&suite__bp_accounting,
 	&suite__wp,
 	&suite__task_exit,
diff --git a/tools/perf/tests/event_refresh.c b/tools/perf/tests/event_refresh.c
new file mode 100644
index 000000000000..726e5de4c795
--- /dev/null
+++ b/tools/perf/tests/event_refresh.c
@@ -0,0 +1,162 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Re-arm a sampling event from its overflow signal handler with
+ * PERF_EVENT_IOC_REFRESH and check that every overflow is delivered.
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <inttypes.h>
+#include <signal.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <sys/mman.h>
+#include <sys/syscall.h>
+#include <linux/perf_event.h>
+
+#include "cloexec.h"
+#include "debug.h"
+#include "tests.h"
+#include "tp_pmu.h"
+#include <internal/lib.h> // page_size
+#include "../perf-sys.h"
+
+#define NR_EVENTS 1000
+/* A real-time signal is queued, so no overflow can be coalesced away. */
+#define REFRESH_SIGNAL (SIGRTMIN + 1)
+
+static volatile sig_atomic_t overflows, hups, refresh_errno;
+
+static void sig_handler(int signum __maybe_unused, siginfo_t *info,
+			void *uc __maybe_unused)
+{
+	int saved_errno = errno;
+
+	overflows++;
+	if (info->si_code == POLL_HUP)
+		hups++;
+	if (ioctl(info->si_fd, PERF_EVENT_IOC_REFRESH, 1) < 0)
+		refresh_errno = errno;
+	errno = saved_errno;
+}
+
+/* Count overflow signals for NR_EVENTS calls of trigger(), period 1. */
+static int count_overflows(struct perf_event_attr *attr, void (*trigger)(int i))
+{
+	struct sigaction sa, old_sa;
+	uint64_t count = 0;
+	int fd, i, err = TEST_FAIL;
+
+	attr->size = sizeof(*attr);
+	attr->sample_period = 1;
+	attr->disabled = 1;
+
+	fd = sys_perf_event_open(attr, 0, -1, -1, perf_event_open_cloexec_flag());
+	if (fd < 0) {
+		int open_errno = errno;
+
+		pr_debug("failed opening event: %s\n", strerror(open_errno));
+		return open_errno == EACCES || open_errno == EPERM ? TEST_SKIP : TEST_FAIL;
+	}
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_sigaction = sig_handler;
+	sa.sa_flags = SA_SIGINFO;
+	if (sigaction(REFRESH_SIGNAL, &sa, &old_sa) < 0) {
+		pr_debug("failed setting up signal handler\n");
+		close(fd);
+		return TEST_FAIL;
+	}
+
+	if (fcntl(fd, F_SETFL, O_RDWR | O_NONBLOCK | O_ASYNC) < 0 ||
+	    fcntl(fd, F_SETSIG, REFRESH_SIGNAL) < 0 ||
+	    fcntl(fd, F_SETOWN, getpid()) < 0) {
+		pr_debug("failed setting up signal delivery: %s\n", strerror(errno));
+		goto out;
+	}
+
+	overflows = 0;
+	hups = 0;
+	refresh_errno = 0;
+	if (ioctl(fd, PERF_EVENT_IOC_REFRESH, 1) < 0) {
+		pr_debug("PERF_EVENT_IOC_REFRESH failed: %s\n", strerror(errno));
+		goto out;
+	}
+	for (i = 0; i < NR_EVENTS; i++)
+		trigger(i);
+	ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
+
+	if (read(fd, &count, sizeof(count)) != sizeof(count))
+		pr_debug("failed to read the event count\n");
+	pr_debug("%d events, count %" PRIu64 ", %d overflows (%d POLL_HUP), re-arm errno %d\n",
+		 NR_EVENTS, count, overflows, hups, refresh_errno);
+	/* Unrelated page faults can only add overflows, never hide one. */
+	if (overflows >= NR_EVENTS)
+		err = TEST_OK;
+out:
+	/* Close first: a late signal must still find our handler. */
+	close(fd);
+	sigaction(REFRESH_SIGNAL, &old_sa, NULL);
+	return err;
+}
+
+static char *pages;
+
+static void touch_page(int i)
+{
+	pages[(long)i * page_size] = 1;
+}
+
+static int test__event_refresh_sw(struct test_suite *test __maybe_unused,
+				  int subtest __maybe_unused)
+{
+	struct perf_event_attr attr = {
+		.type = PERF_TYPE_SOFTWARE,
+		.config = PERF_COUNT_SW_PAGE_FAULTS,
+	};
+	int err;
+
+	pages = mmap(NULL, (long)NR_EVENTS * page_size, PROT_READ | PROT_WRITE,
+		     MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
+	if (pages == MAP_FAILED)
+		return TEST_FAIL;
+	/* One fault per touched page: a huge page would cover many of them. */
+	madvise(pages, (long)NR_EVENTS * page_size, MADV_NOHUGEPAGE);
+
+	err = count_overflows(&attr, touch_page);
+	munmap(pages, (long)NR_EVENTS * page_size);
+	return err;
+}
+
+static void call_getppid(int i __maybe_unused)
+{
+	syscall(SYS_getppid);
+}
+
+static int test__event_refresh_tp(struct test_suite *test __maybe_unused,
+				  int subtest __maybe_unused)
+{
+	struct perf_event_attr attr = {
+		.type = PERF_TYPE_TRACEPOINT,
+	};
+	int id = tp_pmu__id("syscalls", "sys_enter_getppid");
+
+	if (id < 0) {
+		pr_debug("no syscalls:sys_enter_getppid tracepoint\n");
+		return TEST_SKIP;
+	}
+	attr.config = id;
+
+	return count_overflows(&attr, call_getppid);
+}
+
+static struct test_case tests__event_refresh[] = {
+	TEST_CASE_REASON("Software event", event_refresh_sw, "permissions"),
+	TEST_CASE_REASON("Tracepoint event", event_refresh_tp, "permissions"),
+	{	.name = NULL, }
+};
+
+struct test_suite suite__event_refresh = {
+	.desc = "Event re-armed with PERF_EVENT_IOC_REFRESH",
+	.test_cases = tests__event_refresh,
+};
diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
index 5982c4e62cd3..20ae3609892b 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -141,6 +141,7 @@ DECLARE_SUITE(parse_events);
 DECLARE_SUITE(hists_link);
 DECLARE_SUITE(bp_signal);
 DECLARE_SUITE(bp_signal_overflow);
+DECLARE_SUITE(event_refresh);
 DECLARE_SUITE(bp_accounting);
 DECLARE_SUITE(wp);
 DECLARE_SUITE(task_exit);