4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Daniel Vetter <daniel.vetter@xxxxxxxx> [ Upstream commit e73ab00e9a0f1731f34d0620a9c55f5c30c4ad4e ] 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 <chris@xxxxxxxxxxxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Reviewed-by: Sean Paul <seanpaul@xxxxxxxxxxxx> Reported-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> Signed-off-by: Daniel Vetter <daniel.vetter@xxxxxxxxx> Link: http://patchwork.freedesktop.org/patch/msgid/20161218133545.2106-1-daniel.vetter@xxxxxxxx Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- drivers/gpu/drm/drm_connector.c | 20 +++++++++++++++----- include/drm/drm_connector.h | 16 +++++++++++++++- 2 files changed, 30 insertions(+), 6 deletions(-) --- a/drivers/gpu/drm/drm_connector.c +++ b/drivers/gpu/drm/drm_connector.c @@ -225,6 +225,7 @@ int drm_connector_init(struct drm_device INIT_LIST_HEAD(&connector->probed_modes); INIT_LIST_HEAD(&connector->modes); + mutex_init(&connector->mutex); connector->edid_blob_ptr = NULL; connector->status = connector_status_unknown; @@ -359,6 +360,8 @@ void drm_connector_cleanup(struct drm_co connector->funcs->atomic_destroy_state(connector, connector->state); + mutex_destroy(&connector->mutex); + memset(connector, 0, sizeof(*connector)); } EXPORT_SYMBOL(drm_connector_cleanup); @@ -374,14 +377,15 @@ EXPORT_SYMBOL(drm_connector_cleanup); */ int drm_connector_register(struct drm_connector *connector) { - int ret; + int ret = 0; + mutex_lock(&connector->mutex); if (connector->registered) - return 0; + goto unlock; ret = drm_sysfs_connector_add(connector); if (ret) - return ret; + goto unlock; ret = drm_debugfs_connector_add(connector); if (ret) { @@ -397,12 +401,14 @@ int drm_connector_register(struct drm_co drm_mode_object_register(connector->dev, &connector->base); connector->registered = true; - return 0; + goto unlock; err_debugfs: drm_debugfs_connector_remove(connector); err_sysfs: drm_sysfs_connector_remove(connector); +unlock: + mutex_unlock(&connector->mutex); return ret; } EXPORT_SYMBOL(drm_connector_register); @@ -415,8 +421,11 @@ EXPORT_SYMBOL(drm_connector_register); */ void drm_connector_unregister(struct drm_connector *connector) { - if (!connector->registered) + mutex_lock(&connector->mutex); + if (!connector->registered) { + mutex_unlock(&connector->mutex); return; + } if (connector->funcs->early_unregister) connector->funcs->early_unregister(connector); @@ -425,6 +434,7 @@ void drm_connector_unregister(struct drm drm_debugfs_connector_remove(connector); connector->registered = false; + mutex_unlock(&connector->mutex); } EXPORT_SYMBOL(drm_connector_unregister); --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -345,6 +345,8 @@ 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. @@ -359,6 +361,8 @@ 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); @@ -511,7 +515,6 @@ 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 @@ -560,6 +563,13 @@ 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 * be used as an array index. It is invariant over the lifetime of the @@ -572,6 +582,10 @@ 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 */