Fix time/tst-cpuclock1 intermitent failures

This test fails intermittently in systems with heavy load as
CLOCK_PROCESS_CPUTIME_ID is subject to scheduler pressure.  Thus the
test boundaries were relaxed to keep it from failing on such systems.

A refactor of the spent time checking was made with some support
functions.  With the advantage to representing time jitter in percent
of the target.

The values used by the test boundaries are all empirical.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>

diff --git a/support/Makefile b/support/Makefile
index 764b471033350b05c692fd6e2099f328a298e457..e74e0dd519d357412177b04c2fac9849599ba87c 100644 (file)
--- a/support/Makefile
+++ b/support/Makefile
@@ -238,6 +238,7 @@ tests = \
   tst-test_compare \
   tst-test_compare_blob \
   tst-test_compare_string \
+  tst-timespec \
   tst-xreadlink \
   tst-xsigstack \
 

diff --git a/support/timespec.c b/support/timespec.c
index ea6b9475466fd1177151ffe155c3f5d11897c9e5..9f5449e49e8c2d1441f4d6f76913533a1cfecf08 100644 (file)
--- a/support/timespec.c
+++ b/support/timespec.c
@@ -19,6 +19,8 @@
 #include <support/timespec.h>
 #include <stdio.h>
 #include <stdint.h>
+#include <assert.h>
+#include <intprops.h>
 
 void
 test_timespec_before_impl (const char *file, int line,
@@ -57,3 +59,65 @@ test_timespec_equal_or_after_impl (const char *file, int line,
            (intmax_t) diff.tv_sec, (intmax_t) diff.tv_nsec);
   }
 }
+
+/* Convert TIME to nanoseconds stored in a long.
+   Returns long maximum or minimum if the conversion overflows
+   or underflows, respectively.  */
+long
+support_timespec_ns (struct timespec time)
+{
+  long time_ns;
+  if (INT_MULTIPLY_WRAPV(time.tv_sec, TIMESPEC_HZ, &time_ns))
+   {
+      return (time.tv_sec < 0) ? TYPE_MINIMUM(long): TYPE_MAXIMUM(long);
+   }
+  if (INT_ADD_WRAPV(time_ns, time.tv_nsec, &time_ns))
+   {
+      return (time.tv_nsec < 0) ? TYPE_MINIMUM(long): TYPE_MAXIMUM(long);
+   }
+  return time_ns;
+}
+
+/* Returns time normalized timespec with .tv_nsec < TIMESPEC_HZ
+   and the whole seconds  added to .tv_sec. If an overflow or
+   underflow occurs the values are clamped to its maximum or
+   minimum respectively.  */
+struct timespec
+support_timespec_normalize (struct timespec time)
+{
+  struct timespec norm;
+  if (INT_ADD_WRAPV (time.tv_sec, (time.tv_nsec / TIMESPEC_HZ), &norm.tv_sec))
+   {
+     norm.tv_sec = (time.tv_nsec < 0) ? TYPE_MINIMUM (time_t): TYPE_MAXIMUM (time_t);
+     norm.tv_nsec = (time.tv_nsec < 0) ? -1 * (TIMESPEC_HZ - 1) : TIMESPEC_HZ - 1;
+     return norm;
+   }
+  norm.tv_nsec = time.tv_nsec % TIMESPEC_HZ;
+  return norm;
+}
+
+/* Returns TRUE if the observed time is within the given percentage
+   bounds of the expected time, and FALSE otherwise.
+   For example the call
+
+   support_timespec_check_in_range(expected, observed, 0.5, 1.2);
+
+   will check if
+
+   0.5 of expected <= observed <= 1.2 of expected
+
+   In other words it will check if observed time is within 50% to
+   120% of the expected time.  */
+int
+support_timespec_check_in_range (struct timespec expected, struct timespec observed,
+                             double lower_bound, double upper_bound)
+{
+  assert (upper_bound >= lower_bound);
+  long expected_norm, observed_norm;
+  expected_norm = support_timespec_ns (expected);
+  /* Don't divide by zero  */
+  assert(expected_norm != 0);
+  observed_norm = support_timespec_ns (observed);
+  double ratio = (double)observed_norm / expected_norm;
+  return (lower_bound <= ratio && ratio <= upper_bound);
+}

diff --git a/support/timespec.h b/support/timespec.h
index c5852dfe755af149b445c8ef7e7c99560939ff82..fd5466745dc6ae3c9f453afef585831c48c924e7 100644 (file)
--- a/support/timespec.h
+++ b/support/timespec.h
@@ -48,6 +48,14 @@ void test_timespec_equal_or_after_impl (const char *file, int line,
                                         const struct timespec left,
                                         const struct timespec right);
 
+long support_timespec_ns (struct timespec time);
+
+struct timespec support_timespec_normalize (struct timespec time);
+
+int support_timespec_check_in_range (struct timespec expected, struct timespec observed,
+                                 double lower_bound, double upper_bound);
+
+
 /* Check that the timespec on the left represents a time before the
    time on the right. */
 #define TEST_TIMESPEC_BEFORE(left, right)                               \

diff --git a/support/tst-timespec.c b/support/tst-timespec.c
new file mode 100644 (file)
index 0000000..7142355
--- /dev/null
+++ b/support/tst-timespec.c
@@ -0,0 +1,320 @@
+/* Test for support_timespec_check_in_range function.
+   Copyright (C) 2020 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <support/timespec.h>
+#include <support/check.h>
+#include <limits.h>
+
+#define TIMESPEC_HZ 1000000000
+
+struct timespec_ns_test_case
+{
+  struct timespec time;
+  long time_ns;
+};
+
+struct timespec_norm_test_case
+{
+  struct timespec time;
+  struct timespec norm;
+};
+
+struct timespec_test_case
+{
+  struct timespec expected;
+  struct timespec observed;
+  double upper_bound;
+  double lower_bound;
+  int result;
+};
+
+/* Test cases for timespec_ns */
+struct timespec_ns_test_case ns_cases[] = {
+  {.time = {.tv_sec = 0, .tv_nsec = 0},
+   .time_ns = 0,
+  },
+  {.time = {.tv_sec = 0, .tv_nsec = 1},
+   .time_ns = 1,
+  },
+  {.time = {.tv_sec = 1, .tv_nsec = 0},
+   .time_ns = TIMESPEC_HZ,
+  },
+  {.time = {.tv_sec = 1, .tv_nsec = 1},
+   .time_ns = TIMESPEC_HZ + 1,
+  },
+  {.time = {.tv_sec = 0, .tv_nsec = -1},
+   .time_ns = -1,
+  },
+  {.time = {.tv_sec = -1, .tv_nsec = 0},
+   .time_ns = -TIMESPEC_HZ,
+  },
+  {.time = {.tv_sec = -1, .tv_nsec = -1},
+   .time_ns = -TIMESPEC_HZ - 1,
+  },
+  {.time = {.tv_sec = 1, .tv_nsec = -1},
+   .time_ns = TIMESPEC_HZ - 1,
+  },
+  {.time = {.tv_sec = -1, .tv_nsec = 1},
+   .time_ns = -TIMESPEC_HZ + 1,
+  },
+  /* Overflow bondary by 2  */
+  {.time = {.tv_sec = LONG_MAX / TIMESPEC_HZ, .tv_nsec = LONG_MAX%TIMESPEC_HZ - 1},
+   .time_ns = LONG_MAX - 1,
+  },
+  /* Overflow bondary  */
+  {.time = {.tv_sec = LONG_MAX / TIMESPEC_HZ, .tv_nsec = LONG_MAX%TIMESPEC_HZ},
+   .time_ns = LONG_MAX,
+  },
+  /* Underflow bondary by 1  */
+  {.time = {.tv_sec = LONG_MIN / TIMESPEC_HZ, .tv_nsec = LONG_MIN%TIMESPEC_HZ + 1},
+   .time_ns = LONG_MIN + 1,
+  },
+  /* Underflow bondary  */
+  {.time = {.tv_sec = LONG_MIN / TIMESPEC_HZ, .tv_nsec = LONG_MIN%TIMESPEC_HZ},
+   .time_ns = LONG_MIN,
+  },
+  /* Multiplication overflow  */
+  {.time = {.tv_sec = LONG_MAX / TIMESPEC_HZ + 1, .tv_nsec = 1},
+   .time_ns = LONG_MAX,
+  },
+  /* Multiplication underflow  */
+  {.time = {.tv_sec = LONG_MIN / TIMESPEC_HZ - 1, .tv_nsec = -1},
+   .time_ns = LONG_MIN,
+  },
+  /* Sum overflows  */
+  {.time = {.tv_sec = LONG_MAX / TIMESPEC_HZ, .tv_nsec = LONG_MAX%TIMESPEC_HZ + 1},
+   .time_ns = LONG_MAX,
+  },
+  /* Sum underflow  */
+  {.time = {.tv_sec = LONG_MIN / TIMESPEC_HZ, .tv_nsec = LONG_MIN%TIMESPEC_HZ - 1},
+   .time_ns = LONG_MIN,
+  }
+};
+
+/* Test cases for timespec_norm */
+struct timespec_norm_test_case norm_cases[] = {
+  /* Positive cases  */
+  {.time = {.tv_sec = 0, .tv_nsec = 0},
+   .norm = {.tv_sec = 0, .tv_nsec = 0}
+  },
+  {.time = {.tv_sec = 1, .tv_nsec = 0},
+   .norm = {.tv_sec = 1, .tv_nsec = 0}
+  },
+  {.time = {.tv_sec = 0, .tv_nsec = 1},
+   .norm = {.tv_sec = 0, .tv_nsec = 1}
+  },
+  {.time = {.tv_sec = 0, .tv_nsec = TIMESPEC_HZ},
+   .norm = {.tv_sec = 1, .tv_nsec = 0}
+  },
+  {.time = {.tv_sec = 0, .tv_nsec = TIMESPEC_HZ + 1},
+   .norm = {.tv_sec = 1, .tv_nsec = 1}
+  },
+  {.time = {.tv_sec = 1, .tv_nsec = TIMESPEC_HZ},
+   .norm = {.tv_sec = 2, .tv_nsec = 0}
+  },
+  {.time = {.tv_sec = 1, .tv_nsec = TIMESPEC_HZ + 1},
+   .norm = {.tv_sec = 2, .tv_nsec = 1}
+  },
+  /* Negative cases  */
+  {.time = {.tv_sec = 0, .tv_nsec = -TIMESPEC_HZ},
+   .norm = {.tv_sec = -1, .tv_nsec = 0}
+  },
+  {.time = {.tv_sec = 0, .tv_nsec = -TIMESPEC_HZ - 1},
+   .norm = {.tv_sec = -1, .tv_nsec = -1}
+  },
+  {.time = {.tv_sec = -1, .tv_nsec = -TIMESPEC_HZ},
+   .norm = {.tv_sec = -2, .tv_nsec = 0}
+  },
+  {.time = {.tv_sec = -1, .tv_nsec = -TIMESPEC_HZ - 1},
+   .norm = {.tv_sec = -2, .tv_nsec = -1}
+  },
+  /* Overflow bondary by 2  */
+  {.time = {.tv_sec = LONG_MAX - 2, .tv_nsec = TIMESPEC_HZ + 1},
+   .norm = {.tv_sec = LONG_MAX - 1, 1},
+  },
+  /* Overflow bondary by 1  */
+  {.time = {.tv_sec = LONG_MAX - 1, .tv_nsec = TIMESPEC_HZ + 1},
+   .norm = {.tv_sec = LONG_MAX, .tv_nsec = 1},
+  },
+  /* Underflow bondary by 2  */
+  {.time = {.tv_sec = LONG_MIN + 2, .tv_nsec = -TIMESPEC_HZ - 1},
+   .norm = {.tv_sec = LONG_MIN + 1, -1},
+  },
+  /* Underflow bondary by 1  */
+  {.time = {.tv_sec = LONG_MIN + 1, .tv_nsec = -TIMESPEC_HZ - 1},
+   .norm = {.tv_sec = LONG_MIN, .tv_nsec = -1},
+  },
+  /* SUM overflow  */
+  {.time = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ},
+   .norm = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ - 1},
+  },
+  /* SUM underflow  */
+  {.time = {.tv_sec = LONG_MIN, .tv_nsec = -TIMESPEC_HZ},
+   .norm = {.tv_sec = LONG_MIN, .tv_nsec = -1 * (TIMESPEC_HZ - 1)},
+  }
+};
+
+/* Test cases for timespec_check_in_range  */
+struct timespec_test_case check_cases[] = {
+  /* 0 - In range  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 1, .tv_nsec = 0},
+   .upper_bound = 1, .lower_bound = 1, .result = 1,
+  },
+  /* 1 - Out of range  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 2, .tv_nsec = 0},
+   .upper_bound = 1, .lower_bound = 1, .result = 0,
+  },
+  /* 2 - Upper Bound  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 2, .tv_nsec = 0},
+   .upper_bound = 2, .lower_bound = 1, .result = 1,
+  },
+  /* 3 - Lower Bound  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 0, .tv_nsec = 0},
+   .upper_bound = 1, .lower_bound = 0, .result = 1,
+  },
+  /* 4 - Out of range by nanosecs  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 1, .tv_nsec = 500},
+   .upper_bound = 1, .lower_bound = 1, .result = 0,
+  },
+  /* 5 - In range by nanosecs  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 1, .tv_nsec = 50000},
+   .upper_bound = 1.3, .lower_bound = 1, .result = 1,
+  },
+  /* 6 - Big nanosecs  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 0},
+   .observed = {.tv_sec = 0, .tv_nsec = 4000000},
+   .upper_bound = 1, .lower_bound = .001, .result = 1,
+  },
+  /* 7 - In range Negative values  */
+  {.expected = {.tv_sec = -1, .tv_nsec = 0},
+   .observed = {.tv_sec = -1, .tv_nsec = 0},
+   .upper_bound = 1, .lower_bound = 1, .result = 1,
+  },
+  /* 8 - Out of range Negative values  */
+  {.expected = {.tv_sec = -1, .tv_nsec = 0},
+   .observed = {.tv_sec = -1, .tv_nsec = 0},
+   .upper_bound = -1, .lower_bound = -1, .result = 0,
+  },
+  /* 9 - Negative values with negative nanosecs  */
+  {.expected = {.tv_sec = -1, .tv_nsec = 0},
+   .observed = {.tv_sec = -1, .tv_nsec = -2000},
+   .upper_bound = 1, .lower_bound = 1, .result = 0,
+  },
+  /* 10 - Strict bounds  */
+  {.expected = {.tv_sec = -1, .tv_nsec = 0},
+   .observed = {.tv_sec = -1, .tv_nsec = -20000},
+   .upper_bound = 1.00002, .lower_bound = 1.0000191, .result = 1,
+  },
+  /* 11 - Strict bounds with loose upper bound  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 20000},
+   .observed = {.tv_sec = 1, .tv_nsec = 30000},
+   .upper_bound = 1.0000100000, .lower_bound = 1.0000099998, .result = 1,
+  },
+  /* 12 - Strict bounds with loose lower bound  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 20000},
+   .observed = {.tv_sec = 1, .tv_nsec = 30000},
+   .upper_bound = 1.0000099999, .lower_bound = 1.00000999979, .result = 1,
+  },
+  /* 13 - Strict bounds highest precision  */
+  {.expected = {.tv_sec = 1, .tv_nsec = 20000},
+   .observed = {.tv_sec = 1, .tv_nsec = 30000},
+   .upper_bound = 1.00000999980001, .lower_bound = 1.00000999979999, .result = 1,
+  },
+  /* Maximum/Minimum long values  */
+  /* 14  */
+  {.expected = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ - 1},
+   .observed = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ - 2},
+   .upper_bound = 1, .lower_bound = .9, .result = 1,
+  },
+  /* 15 - support_timespec_ns overflow  */
+  {.expected = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ},
+   .observed = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ},
+   .upper_bound = 1, .lower_bound = 1, .result = 1,
+  },
+  /* 16 - support_timespec_ns overflow + underflow  */
+  {.expected = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ},
+   .observed = {.tv_sec = LONG_MIN, .tv_nsec = -TIMESPEC_HZ},
+   .upper_bound = 1, .lower_bound = 1, .result = 0,
+  },
+  /* 17 - support_timespec_ns underflow  */
+  {.expected = {.tv_sec = LONG_MIN, .tv_nsec = -TIMESPEC_HZ},
+   .observed = {.tv_sec = LONG_MIN, .tv_nsec = -TIMESPEC_HZ},
+   .upper_bound = 1, .lower_bound = 1, .result = 1,
+  },
+  /* 18 - support_timespec_ns underflow + overflow  */
+  {.expected = {.tv_sec = LONG_MIN, .tv_nsec = -TIMESPEC_HZ},
+   .observed = {.tv_sec = LONG_MAX, .tv_nsec = TIMESPEC_HZ},
+   .upper_bound = 1, .lower_bound = 1, .result = 0,
+  },
+  /* 19 - Biggest division  */
+  {.expected = {.tv_sec = LONG_MAX / TIMESPEC_HZ , .tv_nsec = TIMESPEC_HZ - 1},
+   .observed = {.tv_sec = 0, .tv_nsec = 1},
+   .upper_bound = 1, .lower_bound = 1.0842021724855044e-19, .result = 1,
+  },
+  /* 20 - Lowest division  */
+  {.expected = {.tv_sec = 0, .tv_nsec = 1},
+   .observed = {.tv_sec = LONG_MAX / TIMESPEC_HZ , .tv_nsec = TIMESPEC_HZ - 1},
+   .upper_bound = LONG_MAX, .lower_bound = 1, .result = 1,
+  },
+};
+
+static int
+do_test (void)
+{
+  int i = 0;
+  int ntests = sizeof (ns_cases) / sizeof (ns_cases[0]);
+
+  printf("Testing support_timespec_ns\n");
+  for (i = 0; i < ntests; i++)
+    {
+      TEST_COMPARE (support_timespec_ns (ns_cases[i].time),
+                   ns_cases[i].time_ns);
+    }
+
+  ntests = sizeof (norm_cases) / sizeof (norm_cases[0]);
+  struct timespec result;
+  printf("Testing support_timespec_normalize\n");
+  for (i = 0; i < ntests; i++)
+    {
+      result = support_timespec_normalize (norm_cases[i].time);
+      TEST_COMPARE (norm_cases[i].norm.tv_sec, result.tv_sec);
+      TEST_COMPARE (norm_cases[i].norm.tv_nsec, result.tv_nsec);
+    }
+
+  ntests = sizeof (check_cases) / sizeof (check_cases[0]);
+  printf("Testing support_timespec_check_in_range\n");
+  for (i = 0; i < ntests; i++)
+    {
+      /* Its hard to find which test failed with just the TEST_COMPARE report.
+         So here we print every running testcase as well.  */
+      printf("Test case %d\n", i);
+      TEST_COMPARE (support_timespec_check_in_range
+                   (check_cases[i].expected, check_cases[i].observed,
+                    check_cases[i].lower_bound,
+                    check_cases[i].upper_bound), check_cases[i].result);
+    }
+  return 0;
+}
+
+#include <support/test-driver.c>

diff --git a/time/tst-cpuclock1.c b/time/tst-cpuclock1.c
index 0120906f23ef15ee6a47563315628def6c688d8c..1ac611a92b733e259a35ee27779300b83ceda524 100644 (file)
--- a/time/tst-cpuclock1.c
+++ b/time/tst-cpuclock1.c
@@ -26,6 +26,7 @@
 #include <signal.h>
 #include <stdint.h>
 #include <sys/wait.h>
+#include <support/timespec.h>
 
 /* This function is intended to rack up both user and system time.  */
 static void
@@ -155,16 +156,12 @@ do_test (void)
   printf ("live PID %d after sleep => %ju.%.9ju\n",
          child, (uintmax_t) after.tv_sec, (uintmax_t) after.tv_nsec);
 
-  struct timespec diff = { .tv_sec = after.tv_sec - before.tv_sec,
-                          .tv_nsec = after.tv_nsec - before.tv_nsec };
-  if (diff.tv_nsec < 0)
-    {
-      --diff.tv_sec;
-      diff.tv_nsec += 1000000000;
-    }
-  if (diff.tv_sec != 0
-      || diff.tv_nsec > 600000000
-      || diff.tv_nsec < 100000000)
+  /* The bound values are empirically defined by testing this code over high cpu
+     usage and different nice values. Of all the values we keep the 90th
+     percentile of values and use those values for our testing allowed range.  */
+  struct timespec diff = timespec_sub (support_timespec_normalize (after),
+                                      support_timespec_normalize (before));
+  if (!support_timespec_check_in_range (sleeptime, diff, .9,  1.1))
     {
       printf ("before - after %ju.%.9ju outside reasonable range\n",
              (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
@@ -194,19 +191,16 @@ do_test (void)
        }
       else
        {
-         struct timespec d = { .tv_sec = afterns.tv_sec - after.tv_sec,
-                               .tv_nsec = afterns.tv_nsec - after.tv_nsec };
-         if (d.tv_nsec < 0)
-           {
-             --d.tv_sec;
-             d.tv_nsec += 1000000000;
-           }
-         if (d.tv_sec > 0
-             || d.tv_nsec < sleeptime.tv_nsec
-             || d.tv_nsec > sleeptime.tv_nsec * 2)
+        /* The bound values are empirically defined by testing this code over
+           high cpu usage and different nice values. Of all the values we keep
+           the 90th percentile of values and use those values for our testing
+           allowed range.  */
+         diff = timespec_sub (support_timespec_normalize (afterns),
+                              support_timespec_normalize (after));
+         if (!support_timespec_check_in_range (sleeptime, diff, .9, 1.2))
            {
              printf ("nanosleep time %ju.%.9ju outside reasonable range\n",
-                     (uintmax_t) d.tv_sec, (uintmax_t) d.tv_nsec);
+                     (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);
              result = 1;
            }
        }
@@ -240,15 +234,13 @@ do_test (void)
   /* Should be close to 0.6.  */
   printf ("dead PID %d => %ju.%.9ju\n",
          child, (uintmax_t) dead.tv_sec, (uintmax_t) dead.tv_nsec);
-
-  diff.tv_sec = dead.tv_sec - after.tv_sec;
-  diff.tv_nsec = dead.tv_nsec - after.tv_nsec;
-  if (diff.tv_nsec < 0)
-    {
-      --diff.tv_sec;
-      diff.tv_nsec += 1000000000;
-    }
-  if (diff.tv_sec != 0 || diff.tv_nsec > 200000000)
+  /* The bound values are empirically defined by testing this code over high cpu
+     usage and different nice values. Of all the values we keep the 90th
+     percentile of values and use those values for our testing allowed range.  */
+  diff = timespec_sub (support_timespec_normalize (dead),
+                      support_timespec_normalize (after));
+  sleeptime.tv_nsec = 100000000;
+  if (!support_timespec_check_in_range (sleeptime, diff, .9, 1.2))
     {
       printf ("dead - after %ju.%.9ju outside reasonable range\n",
              (uintmax_t) diff.tv_sec, (uintmax_t) diff.tv_nsec);