Introduce rwsleep(9), an equivalent to msleep(9) but for code protected

by a write lock.

ok guenther@, vgross@

3 files changed, 65 insertions, 8 deletions

diff --git a/share/man/man9/tsleep.9 b/share/man/man9/tsleep.9
index 391421e86a2..be5cf84d18d 100644
--- a/share/man/man9/tsleep.9
+++ b/share/man/man9/tsleep.9
@@ -1,4 +1,4 @@
-.\"	$OpenBSD: tsleep.9,v 1.10 2015/09/14 15:14:55 schwarze Exp $
+.\"	$OpenBSD: tsleep.9,v 1.11 2016/09/13 08:32:44 mpi Exp $
 .\"	$NetBSD: sleep.9,v 1.11 1999/03/24 06:15:12 mycroft Exp $
 .\"
 .\" Copyright (c) 1996 The NetBSD Foundation, Inc.
@@ -28,12 +28,13 @@
 .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 .\" POSSIBILITY OF SUCH DAMAGE.
 .\"
-.Dd $Mdocdate: September 14 2015 $
+.Dd $Mdocdate: September 13 2016 $
 .Dt TSLEEP 9
 .Os
 .Sh NAME
 .Nm tsleep ,
 .Nm msleep ,
+.Nm rwsleep ,
 .Nm wakeup ,
 .Nm wakeup_n ,
 .Nm wakeup_one
@@ -45,6 +46,8 @@
 .Fn tsleep "void *ident" "int priority" "const char *wmesg" "int timo"
 .Ft int
 .Fn msleep "void *ident" "struct mutex *mtx" "int priority" "const char *wmesg" "int timo"
+.Ft int
+.Fn rwsleep "void *ident" "struct rwlock *wl" "int priority" "const char *wmesg" "int timo"
 .Ft void
 .Fn wakeup "void *ident"
 .Ft void
@@ -53,9 +56,10 @@
 .Fn wakeup_one "void *ident"
 .Sh DESCRIPTION
 These functions implement voluntary context switching.
-.Fn tsleep
-and
+.Fn tsleep ,
 .Fn msleep
+and
+.Fn rwsleep
 are used throughout the kernel whenever processing in the current context
 cannot continue for any of the following reasons:
 .Bl -bullet -offset indent
@@ -146,6 +150,22 @@ argument.
 .El
 .Pp
 The
+.Fn rwsleep
+function behaves just like
+.Fn tsleep ,
+but takes an additional argument:
+.Bl -tag -width priority
+.It Fa wl
+A write lock that will be unlocked when the process is safely
+on the sleep queue.
+The write lock will be relocked at the end of rwsleep unless the
+.Dv PNORELOCK
+flag is set in the
+.Fa priority
+argument.
+.El
+.Pp
+The
 .Fn wakeup
 function will mark all processes which are currently sleeping on the identifier
 .Fa ident
@@ -173,9 +193,10 @@ except that only
 .Fa count
 or one process, respectively, is marked runnable.
 .Sh RETURN VALUES
-.Fn tsleep
-and
+.Fn tsleep ,
 .Fn msleep
+and
+.Fn rwsleep
 return 0 if they return as a result of a
 .Fn wakeup .
 If they return as a result of a signal, the return value is
diff --git a/sys/kern/kern_synch.c b/sys/kern/kern_synch.c
index 4e87d06b64b..beeefe06458 100644
--- a/sys/kern/kern_synch.c
+++ b/sys/kern/kern_synch.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: kern_synch.c,v 1.134 2016/09/03 15:06:06 akfaew Exp $	*/
+/*	$OpenBSD: kern_synch.c,v 1.135 2016/09/13 08:32:44 mpi Exp $	*/
 /*	$NetBSD: kern_synch.c,v 1.37 1996/04/22 01:38:37 christos Exp $	*/
 
 /*
@@ -226,6 +226,40 @@ msleep(const volatile void *ident, struct mutex *mtx, int priority,
 	return (error);
 }
 
+/*
+ * Same as tsleep, but if we have a rwlock provided, then once we've
+ * entered the sleep queue we drop the it. After sleeping we re-lock.
+ */
+int
+rwsleep(const volatile void *ident, struct rwlock *wl, int priority,
+    const char *wmesg, int timo)
+{
+	struct sleep_state sls;
+	int error, error1;
+
+	KASSERT((priority & ~(PRIMASK | PCATCH | PNORELOCK)) == 0);
+	rw_assert_wrlock(wl);
+
+	sleep_setup(&sls, ident, priority, wmesg);
+	sleep_setup_timeout(&sls, timo);
+	sleep_setup_signal(&sls, priority);
+
+	rw_exit_write(wl);
+
+	sleep_finish(&sls, 1);
+	error1 = sleep_finish_timeout(&sls);
+	error = sleep_finish_signal(&sls);
+
+	if ((priority & PNORELOCK) == 0)
+		rw_enter_write(wl);
+
+	/* Signal errors are higher priority than timeouts. */
+	if (error == 0 && error1 != 0)
+		error = error1;
+
+	return (error);
+}
+
 void
 sleep_setup(struct sleep_state *sls, const volatile void *ident, int prio,
     const char *wmesg)
diff --git a/sys/sys/systm.h b/sys/sys/systm.h
index 374805b91b8..36a2e83fd22 100644
--- a/sys/sys/systm.h
+++ b/sys/sys/systm.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: systm.h,v 1.116 2016/09/04 09:22:29 mpi Exp $	*/
+/*	$OpenBSD: systm.h,v 1.117 2016/09/13 08:32:44 mpi Exp $	*/
 /*	$NetBSD: systm.h,v 1.50 1996/06/09 04:55:09 briggs Exp $	*/
 
 /*-
@@ -246,11 +246,13 @@ int	sleep_finish_signal(struct sleep_state *);
 void	sleep_queue_init(void);
 
 struct mutex;
+struct rwlock;
 void    wakeup_n(const volatile void *, int);
 void    wakeup(const volatile void *);
 #define wakeup_one(c) wakeup_n((c), 1)
 int	tsleep(const volatile void *, int, const char *, int);
 int	msleep(const volatile void *, struct mutex *, int,  const char*, int);
+int	rwsleep(const volatile void *, struct rwlock *, int, const char *, int);
 void	yield(void);
 
 void	wdog_register(int (*)(void *, int), void *);