Message-ID: <CAG2KctpSA41wZyZ+9DxpF6st9OY7MWZRzaw9CfidoZctUWqgtw@mail.gmail.com>
Date: Wed, 21 Jan 2026 15:28:37 -0800
From: Samuel Wu <wusamuel@...gle.com>
To: Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc: Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, John Fastabend <john.fastabend@...il.com>, 
	KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, Shuah Khan <shuah@...nel.org>, kernel-team@...roid.com, 
	linux-kernel@...r.kernel.org, bpf@...r.kernel.org, 
	linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 3/4] selftests/bpf: Add tests for wakeup_sources

On Fri, Jan 9, 2026 at 3:32 PM Andrii Nakryiko
<andrii.nakryiko@...il.com> wrote:
>
> On Thu, Jan 8, 2026 at 2:56 PM Samuel Wu <wusamuel@...gle.com> wrote:
> >
> > Sets up the framework to test wakeup_sources iterators using BPF, and
> > adds a few basic tests.
> >
> > Adds several helper functions that for grabbing and releasing a
> > wakelock, abstracting out key functions to setup a framework for testing
> > wakeup_sources.
> >
> > Additionally, adds 3 tests:
> > 1. check_active_count: Checks that stats related to active_count are
> >    properly set after several lock/unlock cycles
> > 2. check_sleep_times: Checks that time accounting related to sleep are
> >    properly calculated
> > 3. check_no_infinite_reads: Checks that the iterator traversal returns
> >    NULL at the end
> >
> > Signed-off-by: Samuel Wu <wusamuel@...gle.com>
> > ---
> >  tools/testing/selftests/bpf/config            |   1 +
> >  .../bpf/prog_tests/wakeup_source_iter.c       | 281 ++++++++++++++++++
> >  .../selftests/bpf/progs/wakeup_source_iter.c  |  70 +++++
> >  3 files changed, 352 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/prog_tests/wakeup_source_iter.c
> >  create mode 100644 tools/testing/selftests/bpf/progs/wakeup_source_iter.c
> >
> > diff --git a/tools/testing/selftests/bpf/config b/tools/testing/selftests/bpf/config
> > index 558839e3c185..c12c5e04b81f 100644
> > --- a/tools/testing/selftests/bpf/config
> > +++ b/tools/testing/selftests/bpf/config
> > @@ -111,6 +111,7 @@ CONFIG_IP6_NF_IPTABLES=y
> >  CONFIG_IP6_NF_FILTER=y
> >  CONFIG_NF_NAT=y
> >  CONFIG_PACKET=y
> > +CONFIG_PM_WAKELOCKS=y
> >  CONFIG_RC_CORE=y
> >  CONFIG_SAMPLES=y
> >  CONFIG_SAMPLE_LIVEPATCH=m
> > diff --git a/tools/testing/selftests/bpf/prog_tests/wakeup_source_iter.c b/tools/testing/selftests/bpf/prog_tests/wakeup_source_iter.c
> > new file mode 100644
> > index 000000000000..31729f11585e
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/prog_tests/wakeup_source_iter.c
> > @@ -0,0 +1,281 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2026 Google LLC */
> > +
> > +#include <test_progs.h>
> > +#include <bpf/libbpf.h>
> > +#include "wakeup_source_iter.skel.h"
> > +
> > +#include <fcntl.h>
> > +#include <stdbool.h>
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +#include <unistd.h>
> > +
> > +
> > +/* Sleep for 10ms to ensure active time is > 0 after converting ns to ms*/
> > +#define TEST_SLEEP_US 10000
> > +#define TEST_SLEEP_MS (TEST_SLEEP_US / 1000)
> > +#define WAKEUP_SOURCE_NAME_LEN 32
> > +
> > +static const char test_ws_name[] = "bpf_selftest_ws";
> > +static bool test_ws_created;
> > +
> > +/*
> > + * Creates a new wakeup source by writing to /sys/power/wake_lock.
> > + * This lock persists until explicitly unlocked.
> > + */
> > +static int lock_ws(const char *name)
> > +{
> > +       int fd;
> > +       ssize_t bytes;
> > +
> > +       fd = open("/sys/power/wake_lock", O_WRONLY);
> > +       if (!ASSERT_OK_FD(fd, "open /sys/power/wake_lock"))
> > +               return -1;
> > +
> > +       bytes = write(fd, name, strlen(name));
> > +       close(fd);
> > +       if (!ASSERT_EQ(bytes, strlen(name), "write to wake_lock"))
> > +               return -1;
> > +
> > +       return 0;
> > +}
> > +
> > +/*
> > + * Destroys the ws by writing the same name to /sys/power/wake_unlock.
> > + */
> > +static void unlock_ws(const char *name)
> > +{
> > +       int fd;
> > +
> > +       fd = open("/sys/power/wake_unlock", O_WRONLY);
> > +       if (!ASSERT_OK_FD(fd, "open /sys/power/wake_unlock"))
> > +               goto cleanup;
> > +
> > +       write(fd, name, strlen(name));
> > +
> > +cleanup:
> > +       if (fd)
> > +               close(fd);
> > +}
> > +
> > +/*
> > + * Setups for testing ws iterators. Will run once prior to suite of tests.
> > + */
> > +static int setup_test_ws(void)
> > +{
> > +       if (lock_ws(test_ws_name))
> > +               return -1;
> > +       test_ws_created = true;
> > +
> > +       return 0;
> > +}
> > +
> > +/*
> > + * Tears down and cleanups testing ws iterators. WIll run once after the suite
> > + * of tests.
> > + */
> > +static void teardown_test_ws(void)
> > +{
> > +       if (!test_ws_created)
> > +               return;
> > +       unlock_ws(test_ws_name);
> > +       test_ws_created = false;
> > +}
> > +
> > +struct WakeupSourceInfo {
> > +       char name[WAKEUP_SOURCE_NAME_LEN];
> > +       unsigned long active_count;
> > +       long active_time_ms;
> > +       unsigned long event_count;
> > +       unsigned long expire_count;
> > +       long last_change_ms;
> > +       long max_time_ms;
> > +       long prevent_sleep_time_ms;
> > +       long total_time_ms;
> > +       unsigned long wakeup_count;
> > +};
> > +
> > +/*
> > + * Reads and parses one wakeup_source record from the iterator file.
> > + * A record is a single space-delimited line.
> > + * Returns true on success, false on EOF. Asserts internally on errors.
> > + */
> > +static bool read_ws_info(FILE *iter_file, struct WakeupSourceInfo *ws_info,
> > +                        char **line)
> > +{
> > +       size_t linesize;
> > +       int items;
> > +
> > +       if (getline(line, &linesize, iter_file) == -1)
> > +               return false;
> > +
> > +       (*line)[strcspn(*line, "\n")] = 0;
> > +
> > +       items = sscanf(*line, "%s %lu %ld %lu %lu %ld %ld %ld %ld %lu",
> > +                      ws_info->name, &ws_info->active_count,
> > +                      &ws_info->active_time_ms, &ws_info->event_count,
> > +                      &ws_info->expire_count, &ws_info->last_change_ms,
> > +                      &ws_info->max_time_ms, &ws_info->prevent_sleep_time_ms,
> > +                      &ws_info->total_time_ms, &ws_info->wakeup_count);
> > +
> > +       if (!ASSERT_EQ(items, 10, "read wakeup source info"))
> > +               return false;
> > +
> > +       if (!ASSERT_LT(strlen(ws_info->name), WAKEUP_SOURCE_NAME_LEN,
> > +                      "name length"))
> > +               return false;
> > +
> > +       return true;
> > +}
> > +
> > +static int get_ws_iter_stream(struct wakeup_source_iter *skel, int *iter_fd,
> > +                             FILE **iter_file)
> > +{
> > +       *iter_fd = bpf_iter_create(
> > +                       bpf_link__fd(skel->links.wakeup_source_collector));
> > +       if (!ASSERT_OK_FD(*iter_fd, "iter_create"))
> > +               return -1;
> > +
> > +       *iter_file = fdopen(*iter_fd, "r");
> > +       if (!ASSERT_OK_PTR(*iter_file, "fdopen"))
> > +               return -1;
> > +
> > +       return 0;
> > +}
> > +
> > +static void subtest_ws_iter_check_active_count(struct wakeup_source_iter *skel)
> > +{
> > +       static const char subtest_ws_name[] = "bpf_selftest_ws_active_count";
> > +       const int lock_unlock_cycles = 5;
> > +       struct WakeupSourceInfo ws_info;
> > +       char *line = NULL;
> > +       bool found_ws = false;
> > +       FILE *iter_file = NULL;
> > +       int iter_fd = -1;
> > +       int i;
> > +
> > +       for (i = 0; i < lock_unlock_cycles; i++) {
> > +               if (!ASSERT_OK(lock_ws(subtest_ws_name), "lock_ws"))
> > +                       goto cleanup;
> > +               unlock_ws(subtest_ws_name);
> > +       }
> > +
> > +       if (!get_ws_iter_stream(skel, &iter_fd, &iter_file))
> > +               goto cleanup;
> > +
> > +       while (read_ws_info(iter_file, &ws_info, &line)) {
> > +               if (strcmp(ws_info.name, subtest_ws_name) == 0) {
> > +                       found_ws = true;
> > +                       ASSERT_EQ(ws_info.active_count, lock_unlock_cycles,
> > +                                 "active_count check");
> > +                       ASSERT_EQ(ws_info.wakeup_count, lock_unlock_cycles,
> > +                                 "wakeup_count check");
> > +                       break;
> > +               }
> > +       }
> > +
> > +       ASSERT_TRUE(found_ws, "found active_count test ws");
> > +
> > +       free(line);
> > +cleanup:
> > +       if (iter_file)
> > +               fclose(iter_file);
> > +       else if (iter_fd >= 0)
> > +               close(iter_fd);
> > +}
> > +
> > +static void subtest_ws_iter_check_sleep_times(struct wakeup_source_iter *skel)
> > +{
> > +       bool found_test_ws = false;
> > +       struct WakeupSourceInfo ws_info;
> > +       char *line = NULL;
> > +       FILE *iter_file;
> > +       int iter_fd;
> > +
> > +       if (!get_ws_iter_stream(skel, &iter_fd, &iter_file))
> > +               goto cleanup;
> > +
> > +       while (read_ws_info(iter_file, &ws_info, &line)) {
> > +               if (strcmp(ws_info.name, test_ws_name) == 0) {
> > +                       found_test_ws = true;
> > +                       ASSERT_GT(ws_info.last_change_ms, 0,
> > +                                 "Expected non-zero last change");
> > +                       ASSERT_GE(ws_info.active_time_ms, TEST_SLEEP_MS,
> > +                                 "Expected active time >= TEST_SLEEP_MS");
> > +                       ASSERT_GE(ws_info.max_time_ms, TEST_SLEEP_MS,
> > +                                 "Expected max time >= TEST_SLEEP_MS");
> > +                       ASSERT_GE(ws_info.total_time_ms, TEST_SLEEP_MS,
> > +                                 "Expected total time >= TEST_SLEEP_MS");
> > +                       break;
> > +               }
> > +       }
> > +
> > +       ASSERT_TRUE(found_test_ws, "found_test_ws");
> > +
> > +       free(line);
> > +cleanup:
> > +       if (iter_file)
> > +               fclose(iter_file);
> > +       else if (iter_fd >= 0)
> > +               close(iter_fd);
> > +}
> > +
> > +static void subtest_ws_iter_check_no_infinite_reads(
> > +               struct wakeup_source_iter *skel)
> > +{
> > +       int iter_fd;
> > +       char buf[256];
> > +
> > +       iter_fd = bpf_iter_create(bpf_link__fd(skel->links.wakeup_source_collector));
> > +       if (!ASSERT_OK_FD(iter_fd, "iter_create"))
> > +               return;
> > +
> > +       while (read(iter_fd, buf, sizeof(buf)) > 0)
> > +               ;
> > +
> > +       /* Final read should return 0 */
> > +       ASSERT_EQ(read(iter_fd, buf, sizeof(buf)), 0, "read");
> > +
> > +       close(iter_fd);
> > +}
> > +
> > +void test_wakeup_source_iter(void)
> > +{
> > +       struct wakeup_source_iter *skel = NULL;
> > +
> > +       if (geteuid() != 0) {
> > +               fprintf(stderr,
> > +                       "Skipping wakeup_source_iter test, requires root\n");
> > +               test__skip();
> > +               return;
> > +       }
> > +
> > +       skel = wakeup_source_iter__open_and_load();
> > +       if (!ASSERT_OK_PTR(skel, "wakeup_source_iter__open_and_load"))
> > +               return;
> > +
> > +       if (!ASSERT_OK(setup_test_ws(), "setup_test_ws"))
> > +               goto destroy;
> > +
> > +       if (!ASSERT_OK(wakeup_source_iter__attach(skel), "skel_attach"))
> > +               goto destroy;
> > +
> > +       /*
> > +        * Sleep on O(ms) to ensure that time stats' resolution isn't lost when
> > +        * converting from ns to ms
> > +        */
> > +       usleep(TEST_SLEEP_US);
> > +
> > +       if (test__start_subtest("active_count"))
> > +               subtest_ws_iter_check_active_count(skel);
> > +       if (test__start_subtest("sleep_times"))
> > +               subtest_ws_iter_check_sleep_times(skel);
> > +       if (test__start_subtest("no_infinite_reads"))
> > +               subtest_ws_iter_check_no_infinite_reads(skel);
> > +
> > +destroy:
> > +       teardown_test_ws();
> > +       wakeup_source_iter__destroy(skel);
> > +}
> > diff --git a/tools/testing/selftests/bpf/progs/wakeup_source_iter.c b/tools/testing/selftests/bpf/progs/wakeup_source_iter.c
> > new file mode 100644
> > index 000000000000..9a377fd28f4e
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/progs/wakeup_source_iter.c
> > @@ -0,0 +1,70 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +/* Copyright (c) 2026 Google LLC */
> > +#include <vmlinux.h>
> > +#include <bpf/bpf_core_read.h>
> > +#include <bpf/bpf_helpers.h>
> > +
> > +#define NSEC_PER_MS 1000000UL
> > +#define WAKEUP_SOURCE_NAME_LEN 32
> > +
> > +char _license[] SEC("license") = "GPL";
> > +
> > +SEC("iter/wakeup_source")
> > +int wakeup_source_collector(struct bpf_iter__wakeup_source *ctx)
> > +{
> > +       const struct wakeup_source *ws = ctx->wakeup_source;
> > +       struct seq_file *seq = ctx->meta->seq;
> > +       char name[WAKEUP_SOURCE_NAME_LEN] = {'\0'};
> > +       const char *pname;
> > +       bool active, autosleep_enable;
> > +       u64 active_count, event_count, expire_count, wakeup_count;
> > +       s64 active_time, curr_time, last_change_time, max_time,
> > +           prevent_sleep_time, start_prevent_time, total_time;
> > +
> > +       if (!ws)
> > +               return 0;
> > +
> > +       active = BPF_CORE_READ_BITFIELD_PROBED(ws, active);
> > +       autosleep_enable = BPF_CORE_READ_BITFIELD_PROBED(ws, autosleep_enabled);
> > +       if (bpf_core_read(&pname, sizeof(pname), &ws->name) ||
> > +           bpf_probe_read_kernel_str(name, sizeof(name), pname) < 0 ||
> > +           bpf_core_read(&active_count, sizeof(active_count), &ws->active_count) ||
> > +           bpf_core_read(&event_count, sizeof(event_count), &ws->event_count) ||
> > +           bpf_core_read(&expire_count, sizeof(expire_count), &ws->expire_count) ||
> > +           bpf_core_read(&last_change_time, sizeof(last_change_time), &ws->last_time) ||
> > +           bpf_core_read(&max_time, sizeof(max_time), &ws->max_time) ||
> > +           bpf_core_read(
> > +               &prevent_sleep_time, sizeof(prevent_sleep_time), &ws->prevent_sleep_time) ||
> > +           bpf_core_read(
> > +               &start_prevent_time, sizeof(start_prevent_time), &ws->start_prevent_time) ||
> > +           bpf_core_read(&total_time, sizeof(total_time), &ws->total_time) ||
> > +           bpf_core_read(&wakeup_count, sizeof(wakeup_count), &ws->wakeup_count))
> > +               return 0;
>
> you really don't need to do this for types returned from iterators,
> try just accessing ws->start_prevent_time (and any other field)
> directly
>

Thanks for reviewing Andrii. That is much cleaner. I'll address this
and the bot's comments in v3.

> > +
> > +
> > +       curr_time = bpf_ktime_get_ns();
> > +       active_time = 0;
> > +       if (active) {
> > +               active_time = curr_time - last_change_time;
> > +               total_time += active_time;
> > +               if (active_time > max_time)
> > +                       max_time = active_time;
> > +               if (autosleep_enable)
> > +                       prevent_sleep_time += curr_time - start_prevent_time;
> > +
> > +       }
> > +
> > +       BPF_SEQ_PRINTF(seq,
> > +                      "%s %lu %ld %lu %lu %ld %ld %ld %ld %lu\n",
> > +                      name,
> > +                      active_count,
> > +                      active_time / NSEC_PER_MS,
> > +                      event_count,
> > +                      expire_count,
> > +                      last_change_time / NSEC_PER_MS,
> > +                      max_time / NSEC_PER_MS,
> > +                      prevent_sleep_time / NSEC_PER_MS,
> > +                      total_time / NSEC_PER_MS,
> > +                      wakeup_count);
> > +       return 0;
> > +}
> > --
> > 2.52.0.457.g6b5491de43-goog
> >

Powered by blists - more mailing lists