From 6c5ed5ae353cdf156f9ac4db17e15db56b4de880 Mon Sep 17 00:00:00 2001 From: Maarten Lankhorst Date: Thu, 6 Apr 2017 20:55:20 +0200 Subject: drm/atomic: Acquire connection_mutex lock in drm_helper_probe_single_connector_modes, v4. mode_valid() called from drm_helper_probe_single_connector_modes() may need to look at connector->state because what a valid mode is may depend on connector properties being set. For example some HDMI modes might be rejected when a connector property forces the connector into DVI mode. Some implementations of detect() already lock all state, so we have to pass an acquire_ctx to them to prevent a deadlock. This means changing the function signature of detect() slightly, and passing the acquire_ctx for locking multiple crtc's. For the callbacks, it will always be non-zero. To allow callers not to worry about this, drm_helper_probe_detect_ctx is added which might handle -EDEADLK for you. Changes since v1: - Always set ctx parameter. Changes since v2: - Always take connection_mutex when probing. Changes since v3: - Remove the ctx from intel_dp_long_pulse, and add WARN_ON(!connection_mutex) (danvet) - Update docs to clarify the locking situation. (danvet) Signed-off-by: Maarten Lankhorst Cc: Boris Brezillon Reviewed-by: Daniel Vetter Link: http://patchwork.freedesktop.org/patch/msgid/1491504920-4017-1-git-send-email-maarten.lankhorst@linux.intel.com --- include/drm/drm_connector.h | 6 ++++++ include/drm/drm_crtc_helper.h | 3 +++ include/drm/drm_modeset_helper_vtables.h | 36 ++++++++++++++++++++++++++++++++ 3 files changed, 45 insertions(+) (limited to 'include') diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h index 941f57f311aa..e2ee74c20b8f 100644 --- a/include/drm/drm_connector.h +++ b/include/drm/drm_connector.h @@ -32,6 +32,7 @@ struct drm_device; struct drm_connector_helper_funcs; +struct drm_modeset_acquire_ctx; struct drm_device; struct drm_crtc; struct drm_encoder; @@ -378,6 +379,11 @@ struct drm_connector_funcs { * the helper library vtable purely for historical reasons. The only DRM * core entry point to probe connector state is @fill_modes. * + * Note that the helper library will already hold + * &drm_mode_config.connection_mutex. Drivers which need to grab additional + * locks to avoid races with concurrent modeset changes need to use + * &drm_connector_helper_funcs.detect_ctx instead. + * * RETURNS: * * drm_connector_status indicating the connector's status. diff --git a/include/drm/drm_crtc_helper.h b/include/drm/drm_crtc_helper.h index 43505c7b2b3f..76e237bd989b 100644 --- a/include/drm/drm_crtc_helper.h +++ b/include/drm/drm_crtc_helper.h @@ -67,6 +67,9 @@ int drm_helper_crtc_mode_set_base(struct drm_crtc *crtc, int x, int y, int drm_helper_probe_single_connector_modes(struct drm_connector *connector, uint32_t maxX, uint32_t maxY); +int drm_helper_probe_detect(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, + bool force); void drm_kms_helper_poll_init(struct drm_device *dev); void drm_kms_helper_poll_fini(struct drm_device *dev); bool drm_helper_hpd_irq_event(struct drm_device *dev); diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h index 091c42205667..7847babd893c 100644 --- a/include/drm/drm_modeset_helper_vtables.h +++ b/include/drm/drm_modeset_helper_vtables.h @@ -747,12 +747,44 @@ struct drm_connector_helper_funcs { * This callback is used by the probe helpers in e.g. * drm_helper_probe_single_connector_modes(). * + * To avoid races with concurrent connector state updates, the helper + * libraries always call this with the &drm_mode_config.connection_mutex + * held. Because of this it's safe to inspect &drm_connector->state. + * * RETURNS: * * The number of modes added by calling drm_mode_probed_add(). */ int (*get_modes)(struct drm_connector *connector); + /** + * @detect_ctx: + * + * Check to see if anything is attached to the connector. The parameter + * force is set to false whilst polling, true when checking the + * connector due to a user request. force can be used by the driver to + * avoid expensive, destructive operations during automated probing. + * + * This callback is optional, if not implemented the connector will be + * considered as always being attached. + * + * This is the atomic version of &drm_connector_funcs.detect. + * + * To avoid races against concurrent connector state updates, the + * helper libraries always call this with ctx set to a valid context, + * and &drm_mode_config.connection_mutex will always be locked with + * the ctx parameter set to this ctx. This allows taking additional + * locks as required. + * + * RETURNS: + * + * &drm_connector_status indicating the connector's status, + * or the error code returned by drm_modeset_lock(), -EDEADLK. + */ + int (*detect_ctx)(struct drm_connector *connector, + struct drm_modeset_acquire_ctx *ctx, + bool force); + /** * @mode_valid: * @@ -771,6 +803,10 @@ struct drm_connector_helper_funcs { * CRTC helpers will not call this function. Drivers therefore must * still fully validate any mode passed in in a modeset request. * + * To avoid races with concurrent connector state updates, the helper + * libraries always call this with the &drm_mode_config.connection_mutex + * held. Because of this it's safe to inspect &drm_connector->state. + * * RETURNS: * * Either &drm_mode_status.MODE_OK or one of the failure reasons in &enum -- cgit v1.2.3