[PATCH 3/4] samples/bpf: Check the error of write() and read()

[Taeung Song <treeze.taeung@gmail.com>]

test_task_rename() and test_urandom_read()
can be failed during write() and read(),
So check the result of them.

Signed-off-by: Taeung Song <treeze.taeung@gmail.com>
---
 samples/bpf/test_overhead_user.c | 20 +++++++++++++++-----
 1 file changed, 15 insertions(+), 5 deletions(-)

diff --git a/samples/bpf/test_overhead_user.c b/samples/bpf/test_overhead_user.c
index 6caf47a..8a88d9c 100644
--- a/samples/bpf/test_overhead_user.c
+++ b/samples/bpf/test_overhead_user.c
@@ -6,6 +6,7 @@
  */
 #define _GNU_SOURCE
 #include <sched.h>
+#include <errno.h>
 #include <stdio.h>
 #include <sys/types.h>
 #include <asm/unistd.h>
@@ -44,8 +45,12 @@ static void test_task_rename(int cpu)
 		exit(1);
 	}
 	start_time = time_get_ns();
-	for (i = 0; i < MAX_CNT; i++)
-		write(fd, buf, sizeof(buf));
+	for (i = 0; i < MAX_CNT; i++) {
+		if (write(fd, buf, sizeof(buf)) < 0) {
+			printf("task rename failed: %s\n", strerror(errno));
+			break;
+		}
+	}
 	printf("task_rename:%d: %lld events per sec\n",
 	       cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
 	close(fd);
@@ -55,7 +60,7 @@ static void test_urandom_read(int cpu)
 {
 	__u64 start_time;
 	char buf[4];
-	int i, fd;
+	int i, fd, err = 0;
 
 	fd = open("/dev/urandom", O_RDONLY);
 	if (fd < 0) {
@@ -63,8 +68,13 @@ static void test_urandom_read(int cpu)
 		exit(1);
 	}
 	start_time = time_get_ns();
-	for (i = 0; i < MAX_CNT; i++)
-		read(fd, buf, sizeof(buf));
+	for (i = 0; i < MAX_CNT; i++) {
+		err = read(fd, buf, sizeof(buf));
+		if (err < 0 || err >= sizeof(buf)) {
+			printf("failed to read from /dev/urandom: %s\n", strerror(errno));
+			break;
+		}
+	}
 	printf("urandom_read:%d: %lld events per sec\n",
 	       cpu, MAX_CNT * 1000000000ll / (time_get_ns() - start_time));
 	close(fd);
-- 
2.7.4