Date: Fri, 2 Jan 2015 13:35:11 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r276534 - head/sys/dev/vt Message-ID: <201501021335.t02DZBRm015072@svn.freebsd.org>
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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.
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