Module Name: src
Committed By: riastradh
Date: Sun Nov 12 19:46:34 UTC 2017
Modified Files:
src/sys/kern: kern_condvar.c
Log Message:
Clarify interpretation of timeout/epsilon in cv_timedwaitbt.
To generate a diff of this commit:
cvs rdiff -u -r1.37 -r1.38 src/sys/kern/kern_condvar.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/kern/kern_condvar.c
diff -u src/sys/kern/kern_condvar.c:1.37 src/sys/kern/kern_condvar.c:1.38
--- src/sys/kern/kern_condvar.c:1.37 Mon Jul 3 02:12:47 2017
+++ src/sys/kern/kern_condvar.c Sun Nov 12 19:46:34 2017
@@ -1,4 +1,4 @@
-/* $NetBSD: kern_condvar.c,v 1.37 2017/07/03 02:12:47 riastradh Exp $ */
+/* $NetBSD: kern_condvar.c,v 1.38 2017/11/12 19:46:34 riastradh Exp $ */
/*-
* Copyright (c) 2006, 2007, 2008 The NetBSD Foundation, Inc.
@@ -34,7 +34,7 @@
*/
#include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: kern_condvar.c,v 1.37 2017/07/03 02:12:47 riastradh Exp $");
+__KERNEL_RCSID(0, "$NetBSD: kern_condvar.c,v 1.38 2017/11/12 19:46:34 riastradh Exp $");
#include <sys/param.h>
#include <sys/systm.h>
@@ -391,20 +391,29 @@ timo2bintime(unsigned timo)
*
* On entry, bt is a timeout in bintime. cv_timedwaitbt subtracts
* the time slept, so on exit, bt is the time remaining after
- * sleeping. No infinite timeout; use cv_wait_sig instead.
+ * sleeping, possibly negative if the complete time has elapsed.
+ * No infinite timeout; use cv_wait_sig instead.
*
* epsilon is a requested maximum error in timeout (excluding
* spurious wakeups). Currently not used, will be used in the
* future to choose between low- and high-resolution timers.
+ * Actual wakeup time will be somewhere in [t, t + max(e, r) + s)
+ * where r is the finest resolution of clock available and s is
+ * scheduling delays for scheduler overhead and competing threads.
+ * Time is measured by the interrupt source implementing the
+ * timeout, not by another timecounter.
*/
int
cv_timedwaitbt(kcondvar_t *cv, kmutex_t *mtx, struct bintime *bt,
- const struct bintime *epsilon __unused)
+ const struct bintime *epsilon __diagused)
{
struct bintime slept;
unsigned start, end;
int error;
+ KASSERTMSG(bt->sec >= 0, "negative timeout");
+ KASSERTMSG(epsilon != NULL, "specify maximum requested delay");
+
/*
* hardclock_ticks is technically int, but nothing special
* happens instead of overflow, so we assume two's-complement
