[PATCH] perf test: Add test for events re-armed with PERF_EVENT_IOC_REFRESH

[PATCH] perf test: Add test for events re-armed with PERF_EVENT_IOC_REFRESH

[Francesco Nigro]

Open a sampling event with sample_period 1, re-arm it with
PERF_EVENT_IOC_REFRESH from its SIGIO 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 tracepoint case fails since
commit 18dbcbfabfff ("perf: Fix the POLL_HUP delivery breakage"):
only the first overflow is delivered. 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.

Link: https://github.com/async-profiler/async-profiler/issues/1813
Signed-off-by: Francesco Nigro <nigro.fra@gmail.com>
---

Notes:
    To run it on any x86_64 box with virtme-ng:
    
      vng --kconfig && make -j$(nproc)
      make -C tools/perf NO_LIBTRACEEVENT=1
      vng -- tools/perf/perf test -v REFRESH
    
    Results, 2 vCPUs:
    
      b320789d6883 (parent)  Tracepoint event: Ok
      18dbcbfabfff           Tracepoint event: FAILED, 1000 events, 1 overflows
      a804c5742bff (master)  Tracepoint event: FAILED, 1000 events, 1 overflows
    
    The software event passes on all three.
    
    Leo Yan's series "perf: Revert direct PMU stop for refresh limit"
    (linux-perf-users, 2026-05-12) reverts 18dbcbfabfff for a different
    reason; I haven't tested it against this.
    
    #regzbot introduced: 18dbcbfabfff

 tools/perf/tests/Build           |   1 +
 tools/perf/tests/builtin-test.c  |   1 +
 tools/perf/tests/event_refresh.c | 136 +++++++++++++++++++++++++++++++
 tools/perf/tests/tests.h         |   1 +
 4 files changed, 139 insertions(+)
 create mode 100644 tools/perf/tests/event_refresh.c

diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
index 66944a4f4..199e10c8c 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 4d0784b16..2b10f4d7f 100644
--- a/tools/perf/tests/builtin-test.c
+++ b/tools/perf/tests/builtin-test.c
@@ -98,6 +98,7 @@ 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 000000000..480f738de
--- /dev/null
+++ b/tools/perf/tests/event_refresh.c
@@ -0,0 +1,136 @@
+// 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 <signal.h>
+#include <stdlib.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
+
+static volatile sig_atomic_t overflows;
+
+static void sig_handler(int signum __maybe_unused, siginfo_t *info,
+			void *uc __maybe_unused)
+{
+	overflows++;
+	ioctl(info->si_fd, PERF_EVENT_IOC_REFRESH, 1);
+}
+
+/* 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;
+	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) {
+		pr_debug("failed opening event: %s\n", strerror(errno));
+		return TEST_SKIP;
+	}
+
+	memset(&sa, 0, sizeof(sa));
+	sa.sa_sigaction = sig_handler;
+	sa.sa_flags = SA_SIGINFO;
+	if (sigaction(SIGIO, &sa, &old_sa) < 0) {
+		pr_debug("failed setting up signal handler\n");
+		goto out_close;
+	}
+
+	fcntl(fd, F_SETFL, O_RDWR | O_NONBLOCK | O_ASYNC);
+	fcntl(fd, F_SETSIG, SIGIO);
+	fcntl(fd, F_SETOWN, getpid());
+
+	overflows = 0;
+	ioctl(fd, PERF_EVENT_IOC_REFRESH, 1);
+	for (i = 0; i < NR_EVENTS; i++)
+		trigger(i);
+	ioctl(fd, PERF_EVENT_IOC_DISABLE, 0);
+
+	pr_debug("%d events, %d overflows\n", NR_EVENTS, overflows);
+	if (overflows == NR_EVENTS)
+		err = TEST_OK;
+
+	sigaction(SIGIO, &old_sa, NULL);
+out_close:
+	close(fd);
+	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;
+
+	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 cee9e6b62..ecc25b5a3 100644
--- a/tools/perf/tests/tests.h
+++ b/tools/perf/tests/tests.h
@@ -124,6 +124,7 @@ 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);
-- 
2.55.0

Re: [PATCH] perf test: Add test for events re-armed with PERF_EVENT_IOC_REFRESH

[Francesco Nigro]

> On systems with Transparent Huge Pages (THP) or multi-size THP (mTHP) set
> to "always" [...] As a result, overflows only reaches 489 (or fewer)
> instead of NR_EVENTS (1000), and count_overflows() returns TEST_FAIL.

Confirmed: on master with transparent_hugepage=always the software case
gets 489 of 1000 overflows. With madvise(MADV_NOHUGEPAGE) on the buffer it
gets all 1000, and the tracepoint case still gets 1. I'll send a v2 with
that change.

Thanks,
Francesco