[bpf,v3,2/2] selftests/bpf: add send_signal_sched_switch test

Added one test, send_signal_sched_switch, to test bpf_send_signal()
helper triggered by sched/sched_switch tracepoint. This test can be used
to verify kernel deadlocks fixed by the previous commit. The test itself
is heavily borrowed from Commit eac9153f2b58 ("bpf/stackmap: Fix deadlock
with rq_lock in bpf_get_stack()").

Cc: Song Liu <songliubraving@fb.com>
Signed-off-by: Yonghong Song <yhs@fb.com>
---
 .../bpf/prog_tests/send_signal_sched_switch.c | 60 +++++++++++++++++++
 .../bpf/progs/test_send_signal_kern.c         |  6 ++
 2 files changed, 66 insertions(+)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c

On Wed, Mar 4, 2020 at 11:11 AM Yonghong Song <yhs@fb.com> wrote:
>
> Added one test, send_signal_sched_switch, to test bpf_send_signal()
> helper triggered by sched/sched_switch tracepoint. This test can be used
> to verify kernel deadlocks fixed by the previous commit. The test itself
> is heavily borrowed from Commit eac9153f2b58 ("bpf/stackmap: Fix deadlock
> with rq_lock in bpf_get_stack()").
>
> Cc: Song Liu <songliubraving@fb.com>
> Signed-off-by: Yonghong Song <yhs@fb.com>
> ---

LGTM.

Acked-by: Andrii Nakryiko <andriin@fb.com>

>  .../bpf/prog_tests/send_signal_sched_switch.c | 60 +++++++++++++++++++
>  .../bpf/progs/test_send_signal_kern.c         |  6 ++
>  2 files changed, 66 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c b/tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c
> new file mode 100644
> index 000000000000..189a34a7addb
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c
> @@ -0,0 +1,60 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <sys/mman.h>
> +#include <pthread.h>
> +#include <sys/types.h>
> +#include <sys/stat.h>
> +#include <fcntl.h>
> +#include "test_send_signal_kern.skel.h"
> +
> +static void sigusr1_handler(int signum)
> +{
> +}
> +
> +#define THREAD_COUNT 100
> +
> +static void *worker(void *p)
> +{
> +       int i;
> +
> +       for ( i = 0; i < 1000; i++)
> +               usleep(1);
> +
> +       return NULL;
> +}
> +
> +void test_send_signal_sched_switch(void)
> +{
> +       struct test_send_signal_kern *skel;
> +       pthread_t threads[THREAD_COUNT];
> +       u32 duration = 0;
> +       int i, err;
> +
> +       signal(SIGUSR1, sigusr1_handler);
> +
> +       skel = test_send_signal_kern__open_and_load();
> +       if (CHECK(!skel, "skel_open_and_load", "skeleton open_and_load failed\n"))
> +               return;
> +
> +       skel->bss->pid = getpid();
> +       skel->bss->sig = SIGUSR1;
> +
> +       err = test_send_signal_kern__attach(skel);
> +       if (CHECK(err, "skel_attach", "skeleton attach failed\n"))
> +               goto destroy_skel;
> +
> +       for (i = 0; i < THREAD_COUNT; i++) {
> +               err = pthread_create(threads + i, NULL, worker, NULL);
> +               if (CHECK(err, "pthread_create", "Error creating thread, %s\n",
> +                         strerror(errno)))
> +                       goto destroy_skel;
> +       }
> +
> +       for (i = 0; i < THREAD_COUNT; i++)
> +               pthread_join(threads[i], NULL);
> +
> +destroy_skel:
> +       test_send_signal_kern__destroy(skel);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
> index 1acc91e87bfc..b4233d3efac2 100644
> --- a/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
> +++ b/tools/testing/selftests/bpf/progs/test_send_signal_kern.c
> @@ -31,6 +31,12 @@ int send_signal_tp(void *ctx)
>         return bpf_send_signal_test(ctx);
>  }
>
> +SEC("tracepoint/sched/sched_switch")
> +int send_signal_tp_sched(void *ctx)
> +{
> +       return bpf_send_signal_test(ctx);
> +}
> +
>  SEC("perf_event")
>  int send_signal_perf(void *ctx)
>  {
> --
> 2.17.1
>