On Tue, Jun 07, 2016 at 05:26:21PM +0200, Thierry Reding wrote:
> From: Thierry Reding <treding@xxxxxxxxxx>
>
> Introduce a new top-level lock for the FB helper code. This will allow
> better locking granularity and avoid the need to abuse modeset locking
> for this purpose instead.
>
> Signed-off-by: Thierry Reding <treding@xxxxxxxxxx>
I think this is now too much locking, and ime too much locking only leads
to massive confusion. It'd be great if we can clean this up (maybe in a
follow-up patch, maybe in this one here) and restrict the core locks to
just where we need them: So all the places that look at probe state need
dev->mode_config.mutex, all the places that change modeset state need the
modeset locks. But e.g. add/remove_one_connector only need the new
fb_helper->lock I think. In the future we might grabbing the other locks
even down into the legacy/atomic fbdev implementations.
> ---
> drivers/gpu/drm/drm_fb_helper.c | 27 ++++++++++++++++++++++++++-
> include/drm/drm_fb_helper.h | 5 +++++
> 2 files changed, 31 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c
> index 252c7557bdb5..f7722bcb0064 100644
> --- a/drivers/gpu/drm/drm_fb_helper.c
> +++ b/drivers/gpu/drm/drm_fb_helper.c
> @@ -105,6 +105,7 @@ static int __drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
> if (!drm_fbdev_emulation)
> return 0;
>
> + WARN_ON(!mutex_is_locked(&fb_helper->lock));
> WARN_ON(!mutex_is_locked(&fb_helper->dev->mode_config.mutex));
>
> count = fb_helper->connector_count + 1;
> @@ -127,6 +128,7 @@ static int __drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
> drm_connector_reference(connector);
> conn->connector = connector;
> fb_helper->connector_info[fb_helper->connector_count++] = conn;
> +
> return 0;
> }
>
> @@ -135,11 +137,13 @@ int drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper,
> {
> int err;
>
> + mutex_lock(&fb_helper->lock);
> mutex_lock(&fb_helper->dev->mode_config.mutex);
>
> err = __drm_fb_helper_add_one_connector(fb_helper, connector);
>
> mutex_unlock(&fb_helper->dev->mode_config.mutex);
> + mutex_unlock(&fb_helper->lock);
>
> return err;
> }
> @@ -168,6 +172,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
> if (!drm_fbdev_emulation)
> return 0;
>
> + mutex_lock(&fb_helper->lock);
> mutex_lock(&dev->mode_config.mutex);
>
> drm_for_each_connector(connector, dev) {
> @@ -184,6 +189,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper)
> }
>
> mutex_unlock(&dev->mode_config.mutex);
> + mutex_unlock(&fb_helper->lock);
>
> return ret;
> }
> @@ -198,6 +204,7 @@ static int __drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
> if (!drm_fbdev_emulation)
> return 0;
>
> + WARN_ON(!mutex_is_locked(&fb_helper->lock));
> WARN_ON(!mutex_is_locked(&fb_helper->dev->mode_config.mutex));
>
> for (i = 0; i < fb_helper->connector_count; i++) {
> @@ -225,11 +232,13 @@ int drm_fb_helper_remove_one_connector(struct drm_fb_helper *fb_helper,
> {
> int err;
>
> + mutex_lock(&fb_helper->lock);
> mutex_lock(&fb_helper->dev->mode_config.mutex);
>
> err = __drm_fb_helper_remove_one_connector(fb_helper, connector);
>
> mutex_unlock(&fb_helper->dev->mode_config.mutex);
> + mutex_unlock(&fb_helper->lock);
>
> return err;
> }
> @@ -478,16 +487,21 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper)
> if (!drm_fbdev_emulation)
> return -ENODEV;
>
> + mutex_lock(&fb_helper->lock);
> drm_modeset_lock_all(dev);
> +
> ret = restore_fbdev_mode(fb_helper);
>
> do_delayed = fb_helper->delayed_hotplug;
> if (do_delayed)
> fb_helper->delayed_hotplug = false;
> +
> drm_modeset_unlock_all(dev);
> + mutex_unlock(&fb_helper->lock);
>
> if (do_delayed)
> drm_fb_helper_hotplug_event(fb_helper);
> +
> return ret;
> }
> EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
> @@ -688,6 +702,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper,
> spin_lock_init(&helper->dirty_lock);
> INIT_WORK(&helper->dirty_work, drm_fb_helper_dirty_work);
> helper->dirty_clip.x1 = helper->dirty_clip.y1 = ~0;
> + mutex_init(&helper->lock);
> helper->funcs = funcs;
> helper->dev = dev;
> }
> @@ -853,6 +868,7 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper)
> unregister_sysrq_key('v', &sysrq_drm_fb_helper_restore_op);
> }
>
> + mutex_destroy(&fb_helper->lock);
> drm_fb_helper_crtc_free(fb_helper);
>
> }
> @@ -2273,16 +2289,20 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
> {
> struct drm_device *dev = fb_helper->dev;
> u32 max_width, max_height;
> + int err = 0;
>
> if (!drm_fbdev_emulation)
> return 0;
>
> + mutex_lock(&fb_helper->lock);
> mutex_lock(&fb_helper->dev->mode_config.mutex);
> +
> if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) {
> fb_helper->delayed_hotplug = true;
> mutex_unlock(&fb_helper->dev->mode_config.mutex);
> - return 0;
> + goto unlock;
> }
> +
> DRM_DEBUG_KMS("\n");
>
> max_width = fb_helper->fb->width;
> @@ -2290,6 +2310,7 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
>
> drm_fb_helper_probe_connector_modes(fb_helper, max_width, max_height);
> mutex_unlock(&fb_helper->dev->mode_config.mutex);
> + mutex_unlock(&fb_helper->lock);
>
> drm_modeset_lock_all(dev);
> drm_setup_crtcs(fb_helper);
> @@ -2297,6 +2318,10 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper)
> drm_fb_helper_set_par(fb_helper->fbdev);
>
> return 0;
> +
> +unlock:
> + mutex_unlock(&fb_helper->lock);
> + return err;
> }
> EXPORT_SYMBOL(drm_fb_helper_hotplug_event);
>
> diff --git a/include/drm/drm_fb_helper.h b/include/drm/drm_fb_helper.h
> index 5b4aa35026a3..7739be08ebca 100644
> --- a/include/drm/drm_fb_helper.h
> +++ b/include/drm/drm_fb_helper.h
> @@ -198,6 +198,11 @@ struct drm_fb_helper {
> struct work_struct dirty_work;
>
> /**
> + * Top-level FB helper lock.
> + */
need to add @lock: in the above comment, otherwise kerneldoc will still
complain about the lack of comment for this new member.
-Daniel
> + struct mutex lock;
> +
> + /**
> * @kernel_fb_list:
> *
> * Entry on the global kernel_fb_helper_list, used for kgdb entry/exit.
> --
> 2.8.3
>
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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