On Wed, Mar 4, 2020 at 9:53 AM Yonghong Song <yhs@xxxxxx> 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@xxxxxx>
> Signed-off-by: Yonghong Song <yhs@xxxxxx>
> ---
> .../bpf/prog_tests/send_signal_sched_switch.c | 89 +++++++++++++++++++
> .../bpf/progs/test_send_signal_kern.c | 6 ++
> 2 files changed, 95 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..f5c9dbdeb173
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/send_signal_sched_switch.c
> @@ -0,0 +1,89 @@
> +// 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 char *filename;
> +
> +static void *worker(void *p)
> +{
> + int err, fd, i = 0;
> + u32 duration = 0;
> + char *pptr;
> + void *ptr;
> +
> + fd = open(filename, O_RDONLY);
> + if (CHECK(fd < 0, "open", "open failed %s\n", strerror(errno)))
> + return NULL;
> +
> + while (i < 100) {
> + struct timespec ts = {0, 1000 + rand() % 2000};
> +
> + ptr = mmap(NULL, 4096 * 64, PROT_READ, MAP_PRIVATE, fd, 0);
> + err = errno;
> + usleep(1);
> + if (CHECK(ptr == MAP_FAILED, "mmap", "mmap failed: %s\n",
> + strerror(err)))
> + break;
> +
> + munmap(ptr, 4096 * 64);
> + usleep(1);
> + pptr = malloc(1);
> + usleep(1);
> + pptr[0] = 1;
> + usleep(1);
> + free(pptr);
> + usleep(1);
> + nanosleep(&ts, NULL);
> + i++;
Any specific reason to do mmap()/munmap() in a loop? Would, say,
getpid syscall work just fine as well to trigger a bunch of context
switches? Or event just usleep(1) alone?
> + }
> + close(fd);
> + 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;
> +
> + filename = "/bin/ls";
> + 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
>
