[PATCH bpf-next] Improve BPF test stability (related to perf events and scheduling)

[Mykola Lysenko <mykolal@fb.com>]

In send_signal, replace sleep with dummy cpu intensive computation
to increase probability of child process being scheduled. Add few
more asserts.

In find_vma, reduce sample_freq as higher values may be rejected in
some qemu setups, remove usleep and increase length of cpu intensive
computation.

In bpf_cookie, perf_link and perf_branches, reduce sample_freq as
higher values may be rejected in some qemu setups

Signed-off-by: Mykola Lysenko <mykolal@fb.com>
---
 .../testing/selftests/bpf/prog_tests/bpf_cookie.c  |  2 +-
 tools/testing/selftests/bpf/prog_tests/find_vma.c  |  5 ++---
 .../selftests/bpf/prog_tests/perf_branches.c       |  4 ++--
 tools/testing/selftests/bpf/prog_tests/perf_link.c |  2 +-
 .../testing/selftests/bpf/prog_tests/send_signal.c | 14 ++++++++++----
 5 files changed, 16 insertions(+), 11 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
index cd10df6cd0fc..0612e79a9281 100644
--- a/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
+++ b/tools/testing/selftests/bpf/prog_tests/bpf_cookie.c
@@ -199,7 +199,7 @@ static void pe_subtest(struct test_bpf_cookie *skel)
 	attr.type = PERF_TYPE_SOFTWARE;
 	attr.config = PERF_COUNT_SW_CPU_CLOCK;
 	attr.freq = 1;
-	attr.sample_freq = 4000;
+	attr.sample_freq = 1000;
 	pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
 	if (!ASSERT_GE(pfd, 0, "perf_fd"))
 		goto cleanup;
diff --git a/tools/testing/selftests/bpf/prog_tests/find_vma.c b/tools/testing/selftests/bpf/prog_tests/find_vma.c
index b74b3c0c555a..acc41223a112 100644
--- a/tools/testing/selftests/bpf/prog_tests/find_vma.c
+++ b/tools/testing/selftests/bpf/prog_tests/find_vma.c
@@ -30,7 +30,7 @@ static int open_pe(void)
 	attr.type = PERF_TYPE_HARDWARE;
 	attr.config = PERF_COUNT_HW_CPU_CYCLES;
 	attr.freq = 1;
-	attr.sample_freq = 4000;
+	attr.sample_freq = 1000;
 	pfd = syscall(__NR_perf_event_open, &attr, 0, -1, -1, PERF_FLAG_FD_CLOEXEC);
 
 	return pfd >= 0 ? pfd : -errno;
@@ -57,7 +57,7 @@ static void test_find_vma_pe(struct find_vma *skel)
 	if (!ASSERT_OK_PTR(link, "attach_perf_event"))
 		goto cleanup;
 
-	for (i = 0; i < 1000000; ++i)
+	for (i = 0; i < 1000000000; ++i)
 		++j;
 
 	test_and_reset_skel(skel, -EBUSY /* in nmi, irq_work is busy */);
@@ -108,7 +108,6 @@ void serial_test_find_vma(void)
 	skel->bss->addr = (__u64)(uintptr_t)test_find_vma_pe;
 
 	test_find_vma_pe(skel);
-	usleep(100000); /* allow the irq_work to finish */
 	test_find_vma_kprobe(skel);
 
 	find_vma__destroy(skel);
diff --git a/tools/testing/selftests/bpf/prog_tests/perf_branches.c b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
index 12c4f45cee1a..bc24f83339d6 100644
--- a/tools/testing/selftests/bpf/prog_tests/perf_branches.c
+++ b/tools/testing/selftests/bpf/prog_tests/perf_branches.c
@@ -110,7 +110,7 @@ static void test_perf_branches_hw(void)
 	attr.type = PERF_TYPE_HARDWARE;
 	attr.config = PERF_COUNT_HW_CPU_CYCLES;
 	attr.freq = 1;
-	attr.sample_freq = 4000;
+	attr.sample_freq = 1000;
 	attr.sample_type = PERF_SAMPLE_BRANCH_STACK;
 	attr.branch_sample_type = PERF_SAMPLE_BRANCH_USER | PERF_SAMPLE_BRANCH_ANY;
 	pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
@@ -151,7 +151,7 @@ static void test_perf_branches_no_hw(void)
 	attr.type = PERF_TYPE_SOFTWARE;
 	attr.config = PERF_COUNT_SW_CPU_CLOCK;
 	attr.freq = 1;
-	attr.sample_freq = 4000;
+	attr.sample_freq = 1000;
 	pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
 	if (CHECK(pfd < 0, "perf_event_open", "err %d\n", pfd))
 		return;
diff --git a/tools/testing/selftests/bpf/prog_tests/perf_link.c b/tools/testing/selftests/bpf/prog_tests/perf_link.c
index ede07344f264..224eba6fef2e 100644
--- a/tools/testing/selftests/bpf/prog_tests/perf_link.c
+++ b/tools/testing/selftests/bpf/prog_tests/perf_link.c
@@ -39,7 +39,7 @@ void serial_test_perf_link(void)
 	attr.type = PERF_TYPE_SOFTWARE;
 	attr.config = PERF_COUNT_SW_CPU_CLOCK;
 	attr.freq = 1;
-	attr.sample_freq = 4000;
+	attr.sample_freq = 1000;
 	pfd = syscall(__NR_perf_event_open, &attr, -1, 0, -1, PERF_FLAG_FD_CLOEXEC);
 	if (!ASSERT_GE(pfd, 0, "perf_fd"))
 		goto cleanup;
diff --git a/tools/testing/selftests/bpf/prog_tests/send_signal.c b/tools/testing/selftests/bpf/prog_tests/send_signal.c
index 776916b61c40..841217bd1df6 100644
--- a/tools/testing/selftests/bpf/prog_tests/send_signal.c
+++ b/tools/testing/selftests/bpf/prog_tests/send_signal.c
@@ -4,11 +4,12 @@
 #include <sys/resource.h>
 #include "test_send_signal_kern.skel.h"
 
-int sigusr1_received = 0;
+int sigusr1_received;
+volatile int volatile_variable;
 
 static void sigusr1_handler(int signum)
 {
-	sigusr1_received++;
+	sigusr1_received = 1;
 }
 
 static void test_send_signal_common(struct perf_event_attr *attr,
@@ -42,7 +43,9 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 		int old_prio;
 
 		/* install signal handler and notify parent */
+		errno = 0;
 		signal(SIGUSR1, sigusr1_handler);
+		ASSERT_OK(errno, "signal");
 
 		close(pipe_c2p[0]); /* close read */
 		close(pipe_p2c[1]); /* close write */
@@ -63,9 +66,12 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 		ASSERT_EQ(read(pipe_p2c[0], buf, 1), 1, "pipe_read");
 
 		/* wait a little for signal handler */
-		sleep(1);
+		for (int i = 0; i < 1000000000; i++)
+			volatile_variable++;
 
 		buf[0] = sigusr1_received ? '2' : '0';
+		ASSERT_EQ(sigusr1_received, 1, "sigusr1_received");
+
 		ASSERT_EQ(write(pipe_c2p[1], buf, 1), 1, "pipe_write");
 
 		/* wait for parent notification and exit */
@@ -110,9 +116,9 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 	ASSERT_EQ(read(pipe_c2p[0], buf, 1), 1, "pipe_read");
 
 	/* trigger the bpf send_signal */
+	skel->bss->signal_thread = signal_thread;
 	skel->bss->pid = pid;
 	skel->bss->sig = SIGUSR1;
-	skel->bss->signal_thread = signal_thread;
 
 	/* notify child that bpf program can send_signal now */
 	ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");
-- 
2.30.2