selftests/proc: Remove idle time monotonicity assertions

Due to broken iowait task counting design (cf: comments above
get_cpu_idle_time_us() and nr_iowait()), it is not possible to provide
the guarantee that /proc/stat or /proc/uptime display monotonic idle
time values.

Remove the assertions that verify the related wrong assumption so that
testers and maintainers don't spend more time on that.

Reported-by: Yu Liao <liaoyu15@huawei.com>
Reported-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/20230222144649.624380-8-frederic@kernel.org

diff --git a/tools/testing/selftests/proc/proc-uptime-001.c b/tools/testing/selftests/proc/proc-uptime-001.c
index 781f7a50fc3f196b95ec31019e744681e60cdd9b..35bddd9dd60b7b3620c76206dd759a9a2adf2050 100644 (file)
--- a/tools/testing/selftests/proc/proc-uptime-001.c
+++ b/tools/testing/selftests/proc/proc-uptime-001.c
@@ -13,7 +13,9 @@
  * 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.
+// Test that boottime value in /proc/uptime increments monotonically.
+// We don't test idle time monotonicity due to broken iowait task
+// counting, cf: comment above get_cpu_idle_time_us()
 #undef NDEBUG
 #include <assert.h>
 #include <stdint.h>
@@ -25,20 +27,18 @@
 
 int main(void)
 {
-       uint64_t start, u0, u1, i0, i1;
+       uint64_t start, u0, u1;
        int fd;
 
        fd = open("/proc/uptime", O_RDONLY);
        assert(fd >= 0);
 
-       proc_uptime(fd, &u0, &i0);
+       u0 = proc_uptime(fd);
        start = u0;
        do {
-               proc_uptime(fd, &u1, &i1);
+               u1 = proc_uptime(fd);
                assert(u1 >= u0);
-               assert(i1 >= i0);
                u0 = u1;
-               i0 = i1;
        } while (u1 - start < 100);
 
        return 0;

diff --git a/tools/testing/selftests/proc/proc-uptime-002.c b/tools/testing/selftests/proc/proc-uptime-002.c
index 7d0aa22bdc12b29b9adf2581b021f84d5ee7b9c2..7ad79d5eaa8440a7fe864ae794081cf1dde0399c 100644 (file)
--- a/tools/testing/selftests/proc/proc-uptime-002.c
+++ b/tools/testing/selftests/proc/proc-uptime-002.c
@@ -13,8 +13,9 @@
  * 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.
+// Test that boottime value in /proc/uptime increments monotonically
+// while shifting across CPUs. We don't test idle time monotonicity
+// due to broken iowait task counting, cf: comment above get_cpu_idle_time_us()
 #undef NDEBUG
 #include <assert.h>
 #include <errno.h>
@@ -45,7 +46,7 @@ int main(void)
        unsigned int len;
        unsigned long *m;
        unsigned int cpu;
-       uint64_t u0, u1, i0, i1;
+       uint64_t u0, u1;
        int fd;
 
        /* find out "nr_cpu_ids" */
@@ -60,7 +61,7 @@ int main(void)
        fd = open("/proc/uptime", O_RDONLY);
        assert(fd >= 0);
 
-       proc_uptime(fd, &u0, &i0);
+       u0 = proc_uptime(fd);
        for (cpu = 0; cpu < len * 8; cpu++) {
                memset(m, 0, len);
                m[cpu / (8 * sizeof(unsigned long))] |= 1UL << (cpu % (8 * sizeof(unsigned long)));
@@ -68,11 +69,9 @@ int main(void)
                /* CPU might not exist, ignore error */
                sys_sched_setaffinity(0, len, m);
 
-               proc_uptime(fd, &u1, &i1);
+               u1 = proc_uptime(fd);
                assert(u1 >= u0);
-               assert(i1 >= i0);
                u0 = u1;
-               i0 = i1;
        }
 
        return 0;

diff --git a/tools/testing/selftests/proc/proc-uptime.h b/tools/testing/selftests/proc/proc-uptime.h
index dc6a42b1d6b077998a31a7b6d5bed1bba64a43f5..ca55abeb0cccca752260b508e3132ab47709ba83 100644 (file)
--- a/tools/testing/selftests/proc/proc-uptime.h
+++ b/tools/testing/selftests/proc/proc-uptime.h
@@ -22,7 +22,7 @@
 
 #include "proc.h"
 
-static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
+static uint64_t proc_uptime(int fd)
 {
        uint64_t val1, val2;
        char buf[64], *p;
@@ -43,18 +43,6 @@ static void proc_uptime(int fd, uint64_t *uptime, uint64_t *idle)
        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);
+       return val1 * 100 + val2;
 }