Re: ia64 clock_gettime and HP_TIMING

[Jes Sorensen <jes at wildopensource dot com>]

Hi,

I didn't hear anything back on this one, so I just wanted to hear if
there were any objections to this patch?

Thanks,
Jes

>>>>> "Jes" == Jes Sorensen <jes@wildopensource.com> writes:

>>>>> "Ulrich" == Ulrich Drepper <drepper@redhat.com> writes:
Ulrich> Jes Sorensen wrote:
>>> Not knowing enough about HPET, my biggest worry is if we have to
>>> open up an extra file descriptor for a permanent mmap of it.

Ulrich> One immediately closes the filedescriptor after the mmap call
Ulrich> if this mmaped region is all that is needed.

Jes> Ok, what about something like this, it makes
Jes> clock_getcpuclokcid() return ENOENT if the itc drifts. I left
Jes> __itc_drift_internal as a global variable as I am not sure
Jes> whether clock_gettime should be change to check it as well before
Jes> allowing a call for CLOCK_PROCESS_CPUTIME_ID.

Jes> I still want to look into supporting the HPET and SN2 RTC at a
Jes> later stage.

2003-12-01  Jes Sorensen  <jes@wildopensource.com>

	* rt/tst-clock.c (do_test): Print message when skipping
	CLOCK_PROCESS_CPUTIME_ID test.
	* sysdeps/unix/sysv/linux/ia64/clock_getcpuclockid.c: New file.
	Provide CLOCK_PROCESS_CPUTIME_ID only if /proc/sal/itc_drift is 0.

--- libc-old/rt/tst-clock.c	6 Jul 2001 04:55:39 -0000	1.3
+++ libc-2.3/rt/tst-clock.c	1 Dec 2003 14:52:07 -0000
@@ -113,6 +113,8 @@
   if (clock_getcpuclockid (0, &cl) == 0)
     /* XXX It's not yet a bug when this fails.  */
     clock_test (cl);
+  else
+	  printf("CPU clock unavailble, skipping test\n");
 
   return result;
 }
--- /dev/null	Wed Dec 31 16:00:00 1969
+++ libc-2.3/sysdeps/unix/sysv/linux/ia64/clock_getcpuclockid.c	Mon Dec  1 06:21:42 2003
@@ -0,0 +1,75 @@
+/* Copyright (C) 2000, 2001, 2003 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, write to the Free
+   Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
+   02111-1307 USA.  */
+
+#include <errno.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <fcntl.h>
+
+int __itc_drift_internal;
+
+int
+clock_getcpuclockid (pid_t pid, clockid_t *clock_id)
+{
+  /* We don't allow any process ID but our own.  */
+  if (pid != 0 && pid != getpid ())
+    return EPERM;
+
+#ifdef CLOCK_PROCESS_CPUTIME_ID
+  {
+    int retval = ENOENT;
+
+    if (__builtin_expect (__itc_drift_internal == 0, 0))
+      {
+	int fd;
+
+	fd = open ("/proc/sal/itc_drift", O_RDONLY);
+	if (__builtin_expect (fd != -1, 1))
+	  {
+	    char buf[16];
+	    ssize_t n;
+	    n = read (fd, buf, sizeof buf);
+	    if (__builtin_expect (n, 1) > 0)
+	      {
+		if (buf[0] != '0')
+		  __itc_drift_internal = 1;
+		else
+		  __itc_drift_internal = -1;
+	      }
+	    close (fd);
+	  }
+	else
+	  __itc_drift_internal = -1;
+      }
+
+    if (__itc_drift_internal != 1)
+      {
+	/* Store the number.  */
+	*clock_id = CLOCK_PROCESS_CPUTIME_ID;
+	retval = 0;
+      }
+
+    return retval;
+  }
+#else
+  /* We don't have a timer for that.  */
+  return ENOENT;
+#endif
+}