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Subject[PATCH -mm] proc: test /proc/uptime
The only tests I could come up with for /proc/uptime are:
* test that values increase monotonically for 1 second,
* bounce around CPUs and test the same thing.

Avoid glibc like plague for affinity given patches like this:
https://marc.info/?l=linux-kernel&m=152130031912594&w=4

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
---

tools/testing/selftests/proc/.gitignore | 2
tools/testing/selftests/proc/Makefile | 2
tools/testing/selftests/proc/proc-uptime-001.c | 45 ++++++++++++++
tools/testing/selftests/proc/proc-uptime-002.c | 79 +++++++++++++++++++++++++
tools/testing/selftests/proc/proc-uptime.h | 74 +++++++++++++++++++++++
5 files changed, 202 insertions(+)

--- a/tools/testing/selftests/proc/.gitignore
+++ b/tools/testing/selftests/proc/.gitignore
@@ -4,4 +4,6 @@
/proc-self-map-files-002
/proc-self-syscall
/proc-self-wchan
+/proc-uptime-001
+/proc-uptime-002
/read
--- a/tools/testing/selftests/proc/Makefile
+++ b/tools/testing/selftests/proc/Makefile
@@ -7,6 +7,8 @@ TEST_GEN_PROGS += proc-self-map-files-001
TEST_GEN_PROGS += proc-self-map-files-002
TEST_GEN_PROGS += proc-self-syscall
TEST_GEN_PROGS += proc-self-wchan
+TEST_GEN_PROGS += proc-uptime-001
+TEST_GEN_PROGS += proc-uptime-002
TEST_GEN_PROGS += read

include ../lib.mk
new file mode 100644
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-uptime-001.c
@@ -0,0 +1,45 @@
+/*
+ * 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 values in /proc/uptime increment monotonically.
+#undef NDEBUG
+#include <assert.h>
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "proc-uptime.h"
+
+int main(void)
+{
+ uint64_t start, u0, u1, i0, i1;
+ int fd;
+
+ fd = open("/proc/uptime", O_RDONLY);
+ assert(fd >= 0);
+
+ proc_uptime(fd, &u0, &i0);
+ start = u0;
+ do {
+ proc_uptime(fd, &u1, &i1);
+ assert(u1 >= u0);
+ assert(i1 >= i0);
+ u0 = u1;
+ i0 = i1;
+ } while (u1 - start < 100);
+
+ return 0;
+}
new file mode 100644
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-uptime-002.c
@@ -0,0 +1,79 @@
+/*
+ * 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 values in /proc/uptime increment monotonically
+// while shifting across CPUs.
+#define _GNU_SOURCE
+#undef NDEBUG
+#include <assert.h>
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <stdint.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+
+#include "proc-uptime.h"
+
+static inline int sys_sched_getaffinity(pid_t pid, unsigned int len, unsigned long *m)
+{
+ return syscall(SYS_sched_getaffinity, pid, len, m);
+}
+
+static inline int sys_sched_setaffinity(pid_t pid, unsigned int len, unsigned long *m)
+{
+ return syscall(SYS_sched_setaffinity, pid, len, m);
+}
+
+int main(void)
+{
+ unsigned int len;
+ unsigned long *m;
+ unsigned int cpu;
+ uint64_t u0, u1, i0, i1;
+ int fd;
+
+ /* find out "nr_cpu_ids" */
+ m = NULL;
+ len = 0;
+ do {
+ len += sizeof(unsigned long);
+ free(m);
+ m = malloc(len);
+ } while (sys_sched_getaffinity(0, len, m) == -EINVAL);
+
+ fd = open("/proc/uptime", O_RDONLY);
+ assert(fd >= 0);
+
+ proc_uptime(fd, &u0, &i0);
+ for (cpu = 0; cpu < len * 8; cpu++) {
+ memset(m, 0, len);
+ m[cpu / (8 * sizeof(unsigned long))] |= 1UL << (cpu % (8 * sizeof(unsigned long)));
+
+ /* CPU might not exist, ignore error */
+ sys_sched_setaffinity(0, len, m);
+
+ proc_uptime(fd, &u1, &i1);
+ assert(u1 >= u0);
+ assert(i1 >= i0);
+ u0 = u1;
+ i0 = i1;
+ }
+
+ return 0;
+}
new file mode 100644
--- /dev/null
+++ b/tools/testing/selftests/proc/proc-uptime.h
@@ -0,0 +1,74 @@
+/*
+ * 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.
+ */
+#undef NDEBUG
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+static unsigned long long xstrtoull(const char *p, char **end)
+{
+ if (*p == '0') {
+ *end = (char *)p + 1;
+ return 0;
+ } else if ('1' <= *p && *p <= '9') {
+ unsigned long long val;
+
+ errno = 0;
+ val = strtoull(p, end, 10);
+ assert(errno == 0);
+ return val;
+ } else
+ assert(0);
+}
+
+static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
+{
+ uint64_t val1, val2;
+ char buf[64], *p;
+ ssize_t rv;
+
+ /* save "p < end" checks */
+ memset(buf, 0, sizeof(buf));
+ rv = pread(fd, buf, sizeof(buf), 0);
+ assert(0 <= rv && rv <= sizeof(buf));
+ buf[sizeof(buf) - 1] = '\0';
+
+ p = buf;
+
+ val1 = xstrtoull(p, &p);
+ assert(p[0] == '.');
+ assert('0' <= p[1] && p[1] <= '9');
+ assert('0' <= p[2] && p[2] <= '9');
+ assert(p[3] == ' ');
+
+ val2 = (p[1] - '0') * 10 + p[2] - '0';
+ *uptime = val1 * 100 + val2;
+
+ p += 4;
+
+ val1 = xstrtoull(p, &p);
+ assert(p[0] == '.');
+ assert('0' <= p[1] && p[1] <= '9');
+ assert('0' <= p[2] && p[2] <= '9');
+ assert(p[3] == '\n');
+
+ val2 = (p[1] - '0') * 10 + p[2] - '0';
+ *idle = val1 * 100 + val2;
+
+ assert(p + 4 == buf + rv);
+}
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