proc: add selftest for last field of /proc/loadavg
Test fork counter formerly known as ->last_pid, the only part of
/proc/loadavg which can be tested.
Testing in init pid namespace is not reliable because of background
activity.
Link: http://lkml.kernel.org/r/20180311152241.GA26247@avx2
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Shuah Khan <shuah@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/tools/testing/selftests/proc/proc-loadavg-001.c b/tools/testing/selftests/proc/proc-loadavg-001.c
new file mode 100644
index 0000000..e38ad6d
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-loadavg-001.c
@@ -0,0 +1,83 @@
+/*
+ * Copyright _ 2018 Alexey Dobriyan <adobriyan@gmail.com>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+/* Test that /proc/loadavg correctly reports last pid in pid namespace. */
+#define _GNU_SOURCE
+#include <errno.h>
+#include <sched.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+int main(void)
+{
+ pid_t pid;
+ int wstatus;
+
+ if (unshare(CLONE_NEWPID) == -1) {
+ if (errno == ENOSYS || errno == EPERM)
+ return 2;
+ return 1;
+ }
+
+ pid = fork();
+ if (pid == -1)
+ return 1;
+ if (pid == 0) {
+ char buf[128], *p;
+ int fd;
+ ssize_t rv;
+
+ fd = open("/proc/loadavg" , O_RDONLY);
+ if (fd == -1)
+ return 1;
+ rv = read(fd, buf, sizeof(buf));
+ if (rv < 3)
+ return 1;
+ p = buf + rv;
+
+ /* pid 1 */
+ if (!(p[-3] == ' ' && p[-2] == '1' && p[-1] == '\n'))
+ return 1;
+
+ pid = fork();
+ if (pid == -1)
+ return 1;
+ if (pid == 0)
+ return 0;
+ if (waitpid(pid, NULL, 0) == -1)
+ return 1;
+
+ lseek(fd, 0, SEEK_SET);
+ rv = read(fd, buf, sizeof(buf));
+ if (rv < 3)
+ return 1;
+ p = buf + rv;
+
+ /* pid 2 */
+ if (!(p[-3] == ' ' && p[-2] == '2' && p[-1] == '\n'))
+ return 1;
+
+ return 0;
+ }
+
+ if (waitpid(pid, &wstatus, 0) == -1)
+ return 1;
+ if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0)
+ return 0;
+ return 1;
+}