From 3db15a3f80f193826e144b1944727a65c13340fe Mon Sep 17 00:00:00 2001
From: Justus Winter <4winter@informatik.uni-hamburg.de>
Date: Sat, 25 Jul 2015 18:23:10 +0200
Subject: kern: add boot-time clock, use it for time stamps

The kernel keeps track of task and thread creation times by saving a
time stamp.  Previously, the real-time clock was used for this.  When
the real-time clock is changed, however, the reference frame for the
time stamps is lost.  This surfaced in Hurd systems reporting
spuriously long uptimes.

Fix this by creating a boot-time clock and use it as reference frame
for the time stamps.

* kern/mach_clock.c (clock_boottime_offset): Create clock by keeping
track of the offset from the real-time.
(clock_boottime_update): New function.
(record_time_stamp): Use the boot-time clock for time stamps.
(read_time_stamp): New function to convert it back to real-time.
(host_set_time): Call `clock_boottime_update'.
* kern/mach_clock.h (record_time_stamp): Amend comment.
(read_time_stamp): New declaration.
* kern/task.c (task_info): Use `read_time_stamp'.
* kern/thread.c (thread_info): Likewise.
---
 kern/thread.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

(limited to 'kern/thread.c')

diff --git a/kern/thread.c b/kern/thread.c
index 1f47553..865a1cc 100644
--- a/kern/thread.c
+++ b/kern/thread.c
@@ -1503,7 +1503,8 @@ kern_return_t thread_info(
 			&basic_info->system_time);
 	    basic_info->base_priority	= thread->priority;
 	    basic_info->cur_priority	= thread->sched_pri;
-	    basic_info->creation_time  = thread->creation_time;
+	    read_time_stamp(&thread->creation_time,
+			    &basic_info->creation_time);
 
 	    /*
 	     *	To calculate cpu_usage, first correct for timer rate,
-- 
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