From b54d64de05084f38af3e475c70d50aa3966cbc2e Mon Sep 17 00:00:00 2001
From: Corinna Vinschen <corinna@vinschen.de>
Date: Mon, 26 Mar 2012 09:05:50 +0000
Subject: [PATCH] 	* hires.h (hires_ms::dmsecs): Drop unused method. 
 * times.cc (JITTER): Remove. 	(gtod): Revert to process-local variable. 
 (hires_ms::nsecs): Just return system time to disallow discrepancy with 
 the OS. 	(hires_ms::resolution): Return coarsest timer value from OS. 
 Add 	comment to explain why. 	(clock_setres): Ditto.

---
 winsup/cygwin/ChangeLog | 11 +++++++++++
 winsup/cygwin/hires.h   |  3 +--
 winsup/cygwin/times.cc  | 39 ++++++++++++++-------------------------
 3 files changed, 26 insertions(+), 27 deletions(-)

diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 3ad68f67a..36b87e67f 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,14 @@
+2012-03-26  Corinna Vinschen  <corinna@vinschen.de>
+
+	* hires.h (hires_ms::dmsecs): Drop unused method.
+	* times.cc (JITTER): Remove.
+	(gtod): Revert to process-local variable.
+	(hires_ms::nsecs): Just return system time to disallow discrepancy with
+	the OS.
+	(hires_ms::resolution): Return coarsest timer value from OS.  Add
+	comment to explain why.
+	(clock_setres): Ditto.
+
 2012-03-21  Christopher Faylor  <me.cygwin2012@cgf.cx>
 
 	* child_info.h: Reset magic number.
diff --git a/winsup/cygwin/hires.h b/winsup/cygwin/hires.h
index 7d84a52cd..c9a4def38 100644
--- a/winsup/cygwin/hires.h
+++ b/winsup/cygwin/hires.h
@@ -1,6 +1,6 @@
 /* hires.h: Definitions for hires clock calculations
 
-   Copyright 2002, 2003, 2004, 2005, 2009, 2010, 2011 Red Hat, Inc.
+   Copyright 2002, 2003, 2004, 2005, 2009, 2010, 2011, 2012 Red Hat, Inc.
 
 This file is part of Cygwin.
 
@@ -62,7 +62,6 @@ class hires_ms : public hires_base
   LONGLONG nsecs ();
   LONGLONG usecs () {return nsecs () / 10LL;}
   LONGLONG msecs () {return nsecs () / 10000LL;}
-  UINT dmsecs () { return timeGetTime_ns () / 10000LL; }
   UINT resolution ();
   LONGLONG uptime () {return (nsecs () - initime_ns) / 10000LL;}
 };
diff --git a/winsup/cygwin/times.cc b/winsup/cygwin/times.cc
index 4f4c39c92..051be82ba 100644
--- a/winsup/cygwin/times.cc
+++ b/winsup/cygwin/times.cc
@@ -1,7 +1,7 @@
 /* times.cc
 
    Copyright 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004,
-   2005, 2006, 2007, 2008, 2009, 2010, 2011 Red Hat, Inc.
+   2005, 2006, 2007, 2008, 2009, 2010, 2011, 2012 Red Hat, Inc.
 
 This file is part of Cygwin.
 
@@ -27,17 +27,7 @@ details. */
 #include "cygtls.h"
 #include "ntdll.h"
 
-/* Max allowed diversion in 100ns of internal timer from system time.  If
-   this difference is exceeded, the internal timer gets re-primed. */
-#define JITTER (40 * 10000LL)
-
-/* TODO: Putting this variable in the shared cygwin region partially solves
-   the problem of cygwin processes not recognizing date changes when other
-   cygwin processes set the date.  There is still an additional problem of
-   long-running cygwin processes becoming confused when a non-cygwin process
-   sets the date.  Unfortunately, it looks like a minor redesign is required
-   to handle that case.  */
-hires_ms gtod __attribute__((section (".cygwin_dll_common"), shared));
+hires_ms NO_COPY gtod;
 
 hires_ns NO_COPY ntod;
 
@@ -575,16 +565,7 @@ hires_ms::nsecs ()
 {
   if (!inited)
     prime ();
-
-  LONGLONG t = systime_ns ();
-  LONGLONG res = initime_ns + timeGetTime_ns ();
-  if (llabs (res - t) > JITTER)
-    {
-      inited = false;
-      prime ();
-      res = initime_ns + timeGetTime_ns ();
-    }
-  return res;
+  return systime_ns ();
 }
 
 extern "C" int
@@ -731,10 +712,15 @@ hires_ms::resolution ()
 
       status = NtQueryTimerResolution (&coarsest, &finest, &actual);
       if (NT_SUCCESS (status))
-	minperiod = (DWORD) actual;
+	/* The actual resolution of the OS timer is a system-wide setting which
+	   can be changed any time, by any process.  The only fixed value we
+	   can rely on is the coarsest value. */
+	minperiod = coarsest;
       else
 	{
-	  /* Try to empirically determine current timer resolution */
+	  /* There's no good reason that NtQueryTimerResolution should fail
+	     at all, but let's play it safe.  Try to empirically determine
+	     current timer resolution */
 	  int priority = GetThreadPriority (GetCurrentThread ());
 	  SetThreadPriority (GetCurrentThread (),
 			     THREAD_PRIORITY_TIME_CRITICAL);
@@ -837,7 +823,10 @@ clock_setres (clockid_t clk_id, struct timespec *tp)
       __seterrno_from_nt_status (status);
       return -1;
     }
-  minperiod = actual;
+  /* The actual resolution of the OS timer is a system-wide setting which
+     can be changed any time, by any process.  The only fixed value we can
+     rely on is the coarsest value. */
+  minperiod = coarsest;
   period_set = true;
   return 0;
 }