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The "vt_suspend_flush_timer()" function is sometimes called locked

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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
This commit is contained in:
hselasky 2015-01-02 13:35:10 +00:00
parent 76a7fec0c1
commit e25dfbc312
1 changed files with 10 additions and 1 deletions
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11
sys/dev/vt/vt_core.c
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@ -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 *vd, int ms)
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 *softc)
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.