From ab843ae81eb445d94ed6821e45df8a782d2886e6 Mon Sep 17 00:00:00 2001
From: Tavian Barnes <tavianator@gmail.com>
Date: Sun, 20 Sep 2009 01:09:24 +0000
Subject: Don't change the `ts' parameter in sandglass_spin.

---
 src/sandglass_impl.h |  2 +-
 src/timespec.c       |  6 +-----
 src/tsc.c            | 15 ++++++++++++++-
 3 files changed, 16 insertions(+), 7 deletions(-)

(limited to 'src')

diff --git a/src/sandglass_impl.h b/src/sandglass_impl.h
index 07a3616..689c6bf 100644
--- a/src/sandglass_impl.h
+++ b/src/sandglass_impl.h
@@ -41,6 +41,6 @@ void sandglass_get_currtime(struct timespec *ts);
 void sandglass_timespec_add(struct timespec *ts, const struct timespec *d);
 void sandglass_timespec_sub(struct timespec *ts, const struct timespec *d);
 int  sandglass_timespec_cmp(const struct timespec *a, const struct timespec *b);
-void sandglass_spin(struct timespec *ts);
+void sandglass_spin(const struct timespec *ts);
 
 #endif /* SANDGLASS_IMPL_H_INCLUDED */
\ No newline at end of file
diff --git a/src/timespec.c b/src/timespec.c
index f8ab791..c077f8b 100644
--- a/src/timespec.c
+++ b/src/timespec.c
@@ -91,7 +91,7 @@ sandglass_timespec_cmp(const struct timespec *a, const struct timespec *b)
 
 /* Spins for the time interval specified by ts */
 void
-sandglass_spin(struct timespec *ts)
+sandglass_spin(const struct timespec *ts)
 {
   struct timespec curr, until;
   sandglass_get_currtime(&curr);
@@ -102,8 +102,4 @@ sandglass_spin(struct timespec *ts)
   do {
     sandglass_get_currtime(&curr);
   } while (sandglass_timespec_cmp(&curr, &until) < 0);
-
-  /* Adjust ts to the time actually waited */
-  sandglass_timespec_sub(&curr, &until);
-  sandglass_timespec_add(ts, &curr);
 }
diff --git a/src/tsc.c b/src/tsc.c
index 554a6d8..135cd2a 100644
--- a/src/tsc.c
+++ b/src/tsc.c
@@ -29,11 +29,24 @@ sandglass_tsc_resolution()
 {
   static long tsc = 0;
   static struct timespec ts = { .tv_sec = 0, .tv_nsec = 10000000L };
+  struct timespec curr, until;
 
   if (tsc == 0) {
+    sandglass_get_currtime(&curr);
+    until = curr;
+    sandglass_timespec_add(&until, &ts);
     tsc = sandglass_get_tsc();
-    sandglass_spin(&ts);
+
+    /* Spin */
+    do {
+      sandglass_get_currtime(&curr);
+    } while (sandglass_timespec_cmp(&curr, &until) < 0);
+
     tsc = sandglass_get_tsc() - tsc;
+
+    /* Adjust ts to the time actually waited */
+    sandglass_timespec_sub(&curr, &until);
+    sandglass_timespec_add(&ts, &curr);
   }
 
   return tsc*1.0e9/ts.tv_nsec;
-- 
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