Author: hselasky
Date: Fri Jan 2 13:35:10 2015
New Revision: 276534
URL: https://svnweb.freebsd.org/changeset/base/276534
Log:
The "vt_suspend_flush_timer()" function is sometimes called locked
which prevents us from doing a "callout_drain()" call. The callout in
question has a lock associated with it and we are not freeing the
callout. That means we can use the "callout_stop()" function to
atomically stop the callback iff the "callout_stop()" function is
called locked. This patch applies proper locking to "callout_stop()"
and replaces a "callout_drain()" with a "callout_stop()".
MFC after: 1 week
Modified:
head/sys/dev/vt/vt_core.c
Modified: head/sys/dev/vt/vt_core.c
==============================================================================
--- head/sys/dev/vt/vt_core.c Fri Jan 2 13:15:36 2015 (r276533)
+++ head/sys/dev/vt/vt_core.c Fri Jan 2 13:35:10 2015 (r276534)
@@ -114,6 +114,7 @@ const struct terminal_class vt_termclass
#define VT_LOCK(vd) mtx_lock(&(vd)->vd_lock)
#define VT_UNLOCK(vd) mtx_unlock(&(vd)->vd_lock)
+#define VT_LOCK_ASSERT(vd, what) mtx_assert(&(vd)->vd_lock, what)
#define VT_UNIT(vw) ((vw)->vw_device->vd_unit * VT_MAXWINDOWS + \
(vw)->vw_number)
@@ -283,12 +284,18 @@ vt_resume_flush_timer(struct vt_device *
static void
vt_suspend_flush_timer(struct vt_device *vd)
{
+ /*
+ * As long as this function is called locked, callout_stop()
+ * has the same effect like callout_drain() with regard to
+ * preventing the callback function from executing.
+ */
+ VT_LOCK_ASSERT(vd, MA_OWNED);
if (!(vd->vd_flags & VDF_ASYNC) ||
!atomic_cmpset_int(&vd->vd_timer_armed, 1, 0))
return;
- callout_drain(&vd->vd_timer);
+ callout_stop(&vd->vd_timer);
}
static void
@@ -2604,7 +2611,9 @@ vt_allocate(struct vt_driver *drv, void
if (vd->vd_flags & VDF_ASYNC) {
/* Stop vt_flush periodic task. */
+ VT_LOCK(vd);
vt_suspend_flush_timer(vd);
+ VT_UNLOCK(vd);
/*
* Mute current terminal until we done. vt_change_font (called
* from vt_resize) will unmute it.
_______________________________________________
svn-src-head@freebsd.org mailing list
http://lists.freebsd.org/mailman/listinfo/svn-src-head
To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
