[src/trunk]: src/sys/rump/librump/rumpkern delay() can't use rumpuser_clock_s...

[pooka <pooka%NetBSD.org@localhost>]

details:   https://anonhg.NetBSD.org/src/rev/9cacd3432be2
branches:  trunk
changeset: 333845:9cacd3432be2
user:      pooka <pooka%NetBSD.org@localhost>
date:      Tue Nov 18 16:57:52 2014 +0000

description:
delay() can't use rumpuser_clock_sleep(), because that may unschedule().

Instead, busyloop with calls to rumpuser_clock_gettime().  Fixing delay()
properly should addressed in hypercall rev.18 by introducing a nowrap
variant/flag for rumpuser_clock_sleep().

diffstat:

 sys/rump/librump/rumpkern/emul.c |  41 ++++++++++++++++++++++++++++++++++++---
 1 files changed, 37 insertions(+), 4 deletions(-)

diffs (76 lines):

diff -r dea56b3ee84f -r 9cacd3432be2 sys/rump/librump/rumpkern/emul.c
--- a/sys/rump/librump/rumpkern/emul.c  Tue Nov 18 13:05:33 2014 +0000
+++ b/sys/rump/librump/rumpkern/emul.c  Tue Nov 18 16:57:52 2014 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: emul.c,v 1.167 2014/11/18 13:05:33 pooka Exp $ */
+/*     $NetBSD: emul.c,v 1.168 2014/11/18 16:57:52 pooka Exp $ */
 
 /*
  * Copyright (c) 2007-2011 Antti Kantee.  All Rights Reserved.
@@ -26,7 +26,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: emul.c,v 1.167 2014/11/18 13:05:33 pooka Exp $");
+__KERNEL_RCSID(0, "$NetBSD: emul.c,v 1.168 2014/11/18 16:57:52 pooka Exp $");
 
 #include <sys/param.h>
 #include <sys/null.h>
@@ -234,11 +234,27 @@
 /*
  * Try to emulate all the MD definitions of DELAY() / delay().
  * Would be nice to fix the #defines in MD headers, but this quicker.
+ *
+ * XXX: we'd need a rumpuser_clock_sleep_nowrap() here.  Since we
+ * don't have it in the current hypercall revision, busyloop.
+ * Note that rather than calibrate a loop delay and work with that,
+ * get call gettime (which does not block) in a loop to make sure
+ * we didn't get virtual ghosttime.  That might be slightly inaccurate
+ * for very small delays ...
+ *
+ * The other option would be to run a thread in the hypervisor which
+ * sleeps for us and we can wait for it using rumpuser_cv_wait_nowrap()
+ * Probably too fussy.  Better just wait for hypercall rev 18 ;)
  */
 static void
 rump_delay(unsigned int us)
 {
-       uint64_t sec, nsec;
+       struct timespec target, tmp;
+       uint64_t sec, sec_ini, sec_now;
+       long nsec, nsec_ini, nsec_now;
+       int loops;
+
+       rumpuser_clock_gettime(RUMPUSER_CLOCK_ABSMONO, &sec_ini, &nsec_ini);
 
 #ifdef __mac68k__
        sec = us / 1000;
@@ -248,10 +264,27 @@
        nsec = (us % 1000000) * 1000;
 #endif
 
+       target.tv_sec = sec_ini;
+       tmp.tv_sec = sec;
+       target.tv_nsec = nsec_ini;
+       tmp.tv_nsec = nsec;
+       timespecadd(&target, &tmp, &target);
+
        if (__predict_false(sec != 0))
                printf("WARNING: over 1s delay\n");
 
-       rumpuser_clock_sleep(RUMPUSER_CLOCK_RELWALL, sec, nsec);
+       for (loops = 0; loops < 1000*1000*100; loops++) {
+               struct timespec cur;
+
+               rumpuser_clock_gettime(RUMPUSER_CLOCK_ABSMONO,
+                   &sec_now, &nsec_now);
+               cur.tv_sec = sec_now;
+               cur.tv_nsec = nsec_now;
+               if (timespeccmp(&cur, &target, >=)) {
+                       return;
+               }
+       }
+       printf("WARNING: DELAY ESCAPED\n");
 }
 void (*delay_func)(unsigned int) = rump_delay;
 __strong_alias(delay,rump_delay);