Re: [PATCH] selftests/bpf: Add ring_buffer__consume_n test.

On Sun, Apr 21, 2024 at 10:11:33PM +0200, Jiri Olsa wrote: ...

...

static struct test_ringbuf_map_key_lskel *skel_map_key; +static struct test_ringbuf_n_lskel *skel_n;

seems like there's no need for this to be static variable

Can you elaborate more? I think we want these pointers to be static to limit the scope to this file, no?

...

static struct test_ringbuf_lskel *skel; static struct ring_buffer *ringbuf; @@ -326,6 +328,67 @@ static void ringbuf_subtest(void) test_ringbuf_lskel__destroy(skel); } +/*

• • Test ring_buffer__consume_n() by producing N_TOT_SAMPLES samples in the ring
• • buffer, via getpid(), and consuming them in chunks of N_SAMPLES.
• */

+#define N_TOT_SAMPLES 32 +#define N_SAMPLES 4

+/* Sample value to verify the callback validity */ +#define SAMPLE_VALUE 42L

+static int process_n_sample(void *ctx, void *data, size_t len) +{

• struct sample *s = data;
• CHECK(s->value != SAMPLE_VALUE,

•      "sample_value", "exp %ld, got %ld\n", SAMPLE_VALUE, s->value);
  

I think we should use ASSERT macros instead in the new code

Good catch, I'll change this to an ASSERT_EQ().

...

• return 0;

+}

+static void ringbuf_n_subtest(void) +{

• int err, i;
• skel_n = test_ringbuf_n_lskel__open();
• if (!ASSERT_OK_PTR(skel_n, "test_ringbuf_n_lskel__open"))

• return;
  

• skel_n->maps.ringbuf.max_entries = getpagesize();
• skel_n->bss->pid = getpid();
• err = test_ringbuf_n_lskel__load(skel_n);
• if (!ASSERT_OK(err, "test_ringbuf_n_lskel__load"))

• goto cleanup;
  

• ringbuf = ring_buffer__new(skel_n->maps.ringbuf.map_fd,

• 		   process_n_sample, NULL, NULL);
  

• if (!ASSERT_OK_PTR(ringbuf, "ring_buffer__new"))

• goto cleanup;
  

• err = test_ringbuf_n_lskel__attach(skel_n);
• if (!ASSERT_OK(err, "test_ringbuf_n_lskel__attach"))

• goto cleanup_ringbuf;
  

• /* Produce N_TOT_SAMPLES samples in the ring buffer by calling getpid() */
• skel->bss->value = SAMPLE_VALUE;

skel_n ?

Absolutely... I'm suprised that it works actually, I guess pure luck (unluck) to reuse the old pointer and have value mapped to the same location. Anyway, I'll fix this.

...

• for (i = 0; i < N_TOT_SAMPLES; i++)

• syscall(__NR_getpgid);
  

• /* Consume all samples from the ring buffer in batches of N_SAMPLES */
• for (i = 0; i < N_TOT_SAMPLES; i += err) {

• err = ring_buffer__consume_n(ringbuf, N_SAMPLES);
  

• ASSERT_EQ(err, N_SAMPLES, "rb_consume");
  

• }

SNIP

...

diff --git a/tools/testing/selftests/bpf/progs/test_ringbuf_n.c b/tools/testing/selftests/bpf/progs/test_ringbuf_n.c new file mode 100644 index 000000000000..b98b5bb20699 --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_ringbuf_n.c @@ -0,0 +1,52 @@ +// SPDX-License-Identifier: GPL-2.0 +// Copyright (c) 2024 Andrea Righi andrea.righi@canonical.com

+#include <linux/bpf.h> +#include <sched.h> +#include <unistd.h> +#include <bpf/bpf_helpers.h> +#include "bpf_misc.h"

+char _license[] SEC("license") = "GPL";

+#define TASK_COMM_LEN 16

+struct sample {

• int pid;
• int seq;

seq does not seem to be checked, is it needed?

seq is not used at all, I can definitely drop it.

Thanks for the review! I'll send a v2.

-Andrea