Re: [PATCH 0/4] Monotonic clock device in GNU Mach

[Pino Toscano]

Hi,

bringing this again, a couple of patches in "dirty form" to get further 
review.

Attached there is my new attempt as it was previously discussed, i.e. 
providing more data in the kernel page of mapped time.

* 01_types.diff:
This adds a new structure in time_value.h, making it named in a similar 
way of stdlib' struct timespec (with the macros of the struct time_value 
provided also for time_spec). I chose to provide a new one, yet 
basically the same as time_value, as it would be awkward to use a 
time_value_t to store nanoseconds in its microseconds member...

* 02_clock.diff:
This patch actually adds the actual new clock, taking care of adding 
microseconds to it, and switching the mapped time struct to the new 
_extended one.

As usual, comments, remarks, etc are welcome.
(I will provide clean git commits with proper changelog once the work i 
finalized.)

Thanks,
-- 
Pino Toscano

--- a/include/mach/time_value.h
+++ b/include/mach/time_value.h
@@ -63,6 +63,39 @@
 }
 
 /*
+ *	Extended time specification.
+ */
+
+struct time_spec {
+	integer_t	seconds;
+	integer_t	nanoseconds;
+};
+typedef	struct time_spec	time_spec_t;
+
+/*
+ *	Macros to manipulate time specs.  Assume that time values
+ *	are normalized (nanoseconds <= 999999999).
+ */
+#define	TIME_NANOS_MAX	(1000000000)
+
+#define	time_spec_add_nsec(val, nanos)	{	\
+	if (((val)->nanoseconds += (nanos))		\
+		>= TIME_NANOS_MAX) {			\
+	    (val)->nanoseconds -= TIME_NANOS_MAX;	\
+	    (val)->seconds++;				\
+	}						\
+}
+
+#define	time_spec_add(result, addend)		{		\
+	(result)->nanoseconds += (addend)->nanoseconds;	\
+	(result)->seconds += (addend)->seconds;			\
+	if ((result)->nanoseconds >= TIME_NANOS_MAX) {	\
+	    (result)->nanoseconds -= TIME_NANOS_MAX;		\
+	    (result)->seconds++;				\
+	}							\
+}
+
+/*
  *	Time value available through the mapped-time interface.
  *	Read this mapped value with
  *		do {
@@ -77,4 +110,14 @@
 	integer_t check_seconds;
 } mapped_time_value_t;
 
+typedef struct mapped_time_value_extended {
+	integer_t seconds;
+	integer_t microseconds;
+	integer_t check_seconds;
+	integer_t version;
+	/* new in version >= 1 */
+	time_spec_t clock_rt; /* realtime clock */
+	time_spec_t clock_mt; /* monotonic clock */
+} mapped_time_value_extended_t;
+           
 #endif	/* _MACH_TIME_VALUE_H_ */

--- a/kern/mach_clock.c
+++ b/kern/mach_clock.c
@@ -69,6 +69,7 @@
 int		hz = HZ;		/* number of ticks per second */
 int		tick = (1000000 / HZ);	/* number of usec per tick */
 time_value_t	time = { 0, 0 };	/* time since bootup (uncorrected) */
+time_value_t	monotonic = { 0, 0 };	/* time since bootup (uncorrected) */
 unsigned long	elapsed_ticks = 0;	/* ticks elapsed since bootup */
 
 int		timedelta = 0;
@@ -93,9 +94,9 @@
  *	We have to insert write fence operations.) FIXME
  */
 
-mapped_time_value_t *mtime = 0;
+mapped_time_value_extended_t *mtime = 0;
 
-#define update_mapped_time(time)				\
+#define update_mapped_time(time, monotonic)			\
 MACRO_BEGIN							\
 	if (mtime != 0) {					\
 		mtime->check_seconds = (time)->seconds;		\
@@ -103,6 +104,16 @@
 		mtime->microseconds = (time)->microseconds;	\
 		asm volatile("":::"memory");			\
 		mtime->seconds = (time)->seconds;		\
+		asm volatile("":::"memory");			\
+		mtime->clock_rt.seconds = (time)->seconds;	\
+		asm volatile("":::"memory");			\
+		mtime->clock_rt.nanoseconds = 			\
+			(time)->microseconds * 1000;		\
+		asm volatile("":::"memory");			\
+		mtime->clock_mt.seconds = (monotonic)->seconds;	\
+		asm volatile("":::"memory");			\
+		mtime->clock_mt.nanoseconds = 			\
+			(monotonic)->microseconds * 1000;	\
 	}							\
 MACRO_END
 
@@ -219,6 +230,7 @@
 	     */
 	    if (timedelta == 0) {
 		time_value_add_usec(&time, usec);
+		time_value_add_usec(&monotonic, usec);
 	    }
 	    else {
 		register int	delta;
@@ -232,8 +244,9 @@
 		    timedelta -= tickdelta;
 		}
 		time_value_add_usec(&time, delta);
+		time_value_add_usec(&monotonic, delta);
 	    }
-	    update_mapped_time(&time);
+	    update_mapped_time(&time, &monotonic);
 
 	    /*
 	     *	Schedule soft-interupt for timeout if needed
@@ -427,7 +440,7 @@
 
 	s = splhigh();
 	time = new_time;
-	update_mapped_time(&time);
+	update_mapped_time(&time, &monotonic);
 	resettodr();
 	splx(s);
 
@@ -498,7 +511,8 @@
 						!= KERN_SUCCESS)
 		panic("mapable_time_init");
 	memset(mtime, 0, PAGE_SIZE);
-	update_mapped_time(&time);
+	mtime->version = 1;
+	update_mapped_time(&time, &monotonic);
 }
 
 int timeopen()

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