Introduce dev_re[lf]thread() functions.

dev_refthread() will return the cdevsw pointer or NULL.  If the
return value is non-NULL a threadcount is held which much be released
with dev_relthread().  If the returned cdevsw is NULL no threadcount
is held on the device.

1 files changed, 25 insertions, 0 deletions

diff --git a/sys/kern/kern_conf.c b/sys/kern/kern_conf.c
index 46fca85..e3e9495 100644
--- a/sys/kern/kern_conf.c
+++ b/sys/kern/kern_conf.c
@@ -84,12 +84,14 @@ dev_lock(void)
 void
 dev_unlock(void)
 {
+
 	mtx_unlock(&devmtx);
 }
 
 void
 dev_ref(struct cdev *dev)
 {
+
 	dev_lock();
 	dev->si_refcount++;
 	dev_unlock();
@@ -107,6 +109,29 @@ dev_rel(struct cdev *dev)
 		freedev(dev);
 	}
 }
+struct cdevsw *
+dev_refthread(struct cdev *dev)
+{
+	struct cdevsw *csw;
+
+	mtx_assert(&devmtx, MA_NOTOWNED);
+	dev_lock();
+	csw = dev->si_devsw;
+	if (csw != NULL)
+		dev->si_threadcount++;
+	dev_unlock();
+	return (csw);
+}
+
+void	
+dev_relthread(struct cdev *dev)
+{
+
+	mtx_assert(&devmtx, MA_NOTOWNED);
+	dev_lock();
+	dev->si_threadcount--;
+	dev_unlock();
+}
 
 int
 nullop(void)