[tor-commits] [tor/maint-0.3.4] Make circuitmux ewma timing test more tolerant on 32bit osx

[nickm at torproject.org]

commit 6e5e1be7375e6e8de38af1f8c2c13e35d745edea
Author: Nick Mathewson <nickm at torproject.org>
Date:   Fri Sep 14 08:40:10 2018 -0400

    Make circuitmux ewma timing test more tolerant on 32bit osx
    
    Since we use a 32-bit approximation for millisecond conversion here,
    we can't expect so much precision.
    
    Fixes part of bug 27139; bugfix on 0.3.4.1-alpha.
---
 src/common/compat_time.h   |  1 +
 src/test/test_circuitmux.c | 13 +++++++++----
 2 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/src/common/compat_time.h b/src/common/compat_time.h
index 57ab20ab1..f241aa5eb 100644
--- a/src/common/compat_time.h
+++ b/src/common/compat_time.h
@@ -196,6 +196,7 @@ monotime_coarse_diff_msec32(const monotime_coarse_t *start,
   // on a 64-bit platform, let's assume 64/64 division is cheap.
   return (int32_t) monotime_coarse_diff_msec(start, end);
 #else
+#define USING_32BIT_MSEC_HACK
   return monotime_coarse_diff_msec32_(start, end);
 #endif
 }
diff --git a/src/test/test_circuitmux.c b/src/test/test_circuitmux.c
index 14c759870..c81d53ae5 100644
--- a/src/test/test_circuitmux.c
+++ b/src/test/test_circuitmux.c
@@ -13,6 +13,8 @@
 #include "scheduler.h"
 #include "test.h"
 
+#include <math.h>
+
 /* XXXX duplicated function from test_circuitlist.c */
 static channel_t *
 new_fake_channel(void)
@@ -103,16 +105,19 @@ test_cmux_compute_ticks(void *arg)
   monotime_coarse_set_mock_time_nsec(now);
   tick = cell_ewma_get_current_tick_and_fraction(&rem);
   tt_uint_op(tick, OP_EQ, tick_zero);
-  tt_double_op(rem, OP_GT, .149999999);
-  tt_double_op(rem, OP_LT, .150000001);
+#ifdef USING_32BIT_MSEC_HACK
+  const double tolerance = .0005;
+#else
+  const double tolerance = .00000001;
+#endif
+  tt_double_op(fabs(rem - .15), OP_LT, tolerance);
 
   /* 25 second later and we should be in another tick. */
   now = START_NS + NS_PER_S * 25;
   monotime_coarse_set_mock_time_nsec(now);
   tick = cell_ewma_get_current_tick_and_fraction(&rem);
   tt_uint_op(tick, OP_EQ, tick_zero + 2);
-  tt_double_op(rem, OP_GT, .499999999);
-  tt_double_op(rem, OP_LT, .500000001);
+  tt_double_op(fabs(rem - .5), OP_LT, tolerance);
 
  done:
   ;