svn commit: r276534 - head/sys/dev/vt
John Baldwin
jhb at FreeBSD.org
Mon Jan 5 17:37:10 UTC 2015
On 1/2/15 8:35 AM, Hans Petter Selasky wrote:
> 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()".
>
> 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);
Note that this assert is redundant. callout_stop() already asserts this
for a callout initialized via callout_init_mtx().
>
> 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
--
John Baldwin
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