From 4e5b54f127426c82dc2816340c26d951a5bb3429 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Sun, 18 Dec 2016 14:35:45 +0100 Subject: drm: prevent double-(un)registration for connectors If we're unlucky then the registration from a hotplugged connector might race with the final registration step on driver load. And since MST topology discover is asynchronous that's even somewhat likely. v2: Also update the kerneldoc for @registered! v3: Review from Chris: - Improve kerneldoc for late_register/early_unregister callbacks. - Use mutex_destroy. Reviewed-by: Chris Wilson Cc: Chris Wilson Reviewed-by: Sean Paul Reported-by: Chris Wilson Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/20161218133545.2106-1-daniel.vetter@ffwll.ch (cherry picked from commit e73ab00e9a0f1731f34d0620a9c55f5c30c4ad4e) --- include/drm/drm_connector.h | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index a9b95246e26e..045a97cbeba2 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -381,6 +381,8 @@ struct drm_connector_funcs { * core drm connector interfaces. Everything added from this callback * should be unregistered in the early_unregister callback. * + * This is called while holding drm_connector->mutex. + * * Returns: * * 0 on success, or a negative error code on failure. @@ -395,6 +397,8 @@ struct drm_connector_funcs { * late_register(). It is called from drm_connector_unregister(), * early in the driver unload sequence to disable userspace access * before data structures are torndown. + * + * This is called while holding drm_connector->mutex. */ void (*early_unregister)(struct drm_connector *connector); @@ -559,7 +563,6 @@ struct drm_cmdline_mode { * @interlace_allowed: can this connector handle interlaced modes? * @doublescan_allowed: can this connector handle doublescan? * @stereo_allowed: can this connector handle stereo modes? - * @registered: is this connector exposed (registered) with userspace? * @modes: modes available on this connector (from fill_modes() + user) * @status: one of the drm_connector_status enums (connected, not, or unknown) * @probed_modes: list of modes derived directly from the display @@ -607,6 +610,13 @@ struct drm_connector { char *name; + /** + * @mutex: Lock for general connector state, but currently only protects + * @registered. Most of the connector state is still protected by the + * mutex in &drm_mode_config. + */ + struct mutex mutex; + /** * @index: Compacted connector index, which matches the position inside * the mode_config.list for drivers not supporting hot-add/removing. Can @@ -620,6 +630,10 @@ struct drm_connector { bool interlace_allowed; bool doublescan_allowed; bool stereo_allowed; + /** + * @registered: Is this connector exposed (registered) with userspace? + * Protected by @mutex. + */ bool registered; struct list_head modes; /* list of modes on this connector */ -- cgit v1.2.3 From e6e7b48b295afa5a5ab440de0a94d9ad8b3ce2d0 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 12 Jan 2017 17:15:56 +0100 Subject: drm: Don't race connector registration I was under the misconception that the sysfs dev stuff can be fully set up, and then registered all in one step with device_add. That's true for properties and property groups, but not for parents and child devices. Those must be fully registered before you can register a child. Add a bit of tracking to make sure that asynchronous mst connector hotplugging gets this right. For consistency we rely upon the implicit barriers of the connector->mutex, which is taken anyway, to ensure that at least either the connector or device registration call will work out. Mildly tested since I can't reliably reproduce this on my mst box here. Reported-by: Dave Hansen Cc: Dave Hansen Acked-by: Chris Wilson Cc: Chris Wilson Signed-off-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1484237756-2720-1-git-send-email-daniel.vetter@ffwll.ch --- include/drm/drmP.h | 1 + 1 file changed, 1 insertion(+) (limited to 'include') diff --git a/include/drm/drmP.h b/include/drm/drmP.h index 192016e2b518..9c4ee144b5f6 100644 --- a/include/drm/drmP.h +++ b/include/drm/drmP.h @@ -517,6 +517,7 @@ struct drm_device { struct drm_minor *control; /**< Control node */ struct drm_minor *primary; /**< Primary node */ struct drm_minor *render; /**< Render node */ + bool registered; /* currently active master for this device. Protected by master_mutex */ struct drm_master *master; -- cgit v1.2.3