On 3/4/20 10:30 AM, Song Liu wrote:
On Mar 4, 2020, at 10:12 AM, Yonghong Song <yhs@xxxxxx> wrote:
On 3/4/20 10:08 AM, Andrii Nakryiko wrote:
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?
No particular reason. Copied from Song's original reproducer and
it is working. Maybe Song can comment why it is written this way.
In that test, mmap/munmap are used to lock mmap_sem. I guess we
don't really need them in this test.
Thanks. I will simplify the test then. The goal is to get more context
switches.
Thanks,
song
