Improve BPF test stability (related to perf events and scheduling)

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 <[email protected]>

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;

tools/testing/selftests/bpf/prog_tests/find_vma.c

@@ -30,12 +30,20 @@ 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;
 }
 
+static bool find_vma_pe_condition(struct find_vma *skel)
+{
+	return skel->bss->found_vm_exec != 1 ||
+		skel->data->find_addr_ret == -1 ||
+		skel->data->find_zero_ret != 0 ||
+		skel->bss->d_iname[0] == 0;
+}
+
 static void test_find_vma_pe(struct find_vma *skel)
 {
 	struct bpf_link *link = NULL;
@@ -57,7 +65,7 @@ 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 && find_vma_pe_condition(skel); ++i)
 		++j;
 
 	test_and_reset_skel(skel, -EBUSY /* in nmi, irq_work is busy */);
@@ -108,7 +116,6 @@ 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);

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;

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;

tools/testing/selftests/bpf/prog_tests/send_signal.c

@@ -4,11 +4,11 @@
 #include <sys/resource.h>
 #include "test_send_signal_kern.skel.h"
 
-int sigusr1_received = 0;
+static int sigusr1_received;
 
 static void sigusr1_handler(int signum)
 {
-	sigusr1_received++;
+	sigusr1_received = 1;
 }
 
 static void test_send_signal_common(struct perf_event_attr *attr,
@@ -40,9 +40,10 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 
 	if (pid == 0) {
 		int old_prio;
+		volatile int volatile_variable = 0;
 
 		/* install signal handler and notify parent */
-		signal(SIGUSR1, sigusr1_handler);
+		ASSERT_NEQ(signal(SIGUSR1, sigusr1_handler), SIG_ERR, "signal");
 
 		close(pipe_c2p[0]); /* close read */
 		close(pipe_p2c[1]); /* close write */
@@ -63,9 +64,11 @@ 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 < 100000000 && !sigusr1_received; i++)
+			volatile_variable /= i + 1;
 
 		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 */
@@ -93,7 +96,7 @@ static void test_send_signal_common(struct perf_event_attr *attr,
 			goto destroy_skel;
 		}
 	} else {
-		pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1,
+		pmu_fd = syscall(__NR_perf_event_open, attr, pid, -1 /* cpu */,
 				 -1 /* group id */, 0 /* flags */);
 		if (!ASSERT_GE(pmu_fd, 0, "perf_event_open")) {
 			err = -1;
@@ -110,9 +113,9 @@ 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->pid = pid;
-	skel->bss->sig = SIGUSR1;
 	skel->bss->signal_thread = signal_thread;
+	skel->bss->sig = SIGUSR1;
+	skel->bss->pid = pid;
 
 	/* notify child that bpf program can send_signal now */
 	ASSERT_EQ(write(pipe_p2c[1], buf, 1), 1, "pipe_write");

tools/testing/selftests/bpf/progs/test_send_signal_kern.c

@@ -10,7 +10,7 @@ static __always_inline int bpf_send_signal_test(void *ctx)
 {
 	int ret;
 
-	if (status != 0 || sig == 0 || pid == 0)
+	if (status != 0 || pid == 0)
 		return 0;
 
 	if ((bpf_get_current_pid_tgid() >> 32) == pid) {