Date: Sun, 11 Jan 2015 12:25:10 +0000 (UTC) From: Hans Petter Selasky <hselasky@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-10@freebsd.org Subject: svn commit: r276972 - stable/10/sys/dev/vt Message-ID: <201501111225.t0BCPAKg091291@svn.freebsd.org>
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Author: hselasky Date: Sun Jan 11 12:25:10 2015 New Revision: 276972 URL: https://svnweb.freebsd.org/changeset/base/276972 Log: MFC r276534: 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: stable/10/sys/dev/vt/vt_core.c Directory Properties: stable/10/ (props changed) Modified: stable/10/sys/dev/vt/vt_core.c ============================================================================== --- stable/10/sys/dev/vt/vt_core.c Sun Jan 11 12:21:39 2015 (r276971) +++ stable/10/sys/dev/vt/vt_core.c Sun Jan 11 12:25:10 2015 (r276972) @@ -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) @@ -282,12 +283,18 @@ 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 @@ -2595,7 +2602,9 @@ 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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