| Message ID | 20170321081358.27237-6-thierry.reding@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Tue, Mar 21, 2017 at 09:13:53AM +0100, Thierry Reding wrote: > From: Thierry Reding <treding@nvidia.com> > > 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. > > Tested-by: John Stultz <john.stultz@linaro.org> > Signed-off-by: Thierry Reding <treding@nvidia.com> Some suggestions below, since I think this state of locking implemented here is a bit a too awkwared intermediate thing. > --- > drivers/gpu/drm/drm_fb_helper.c | 27 ++++++++++++++++++++++++++- > include/drm/drm_fb_helper.h | 7 +++++++ > 2 files changed, 33 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > index 6af80afc4f40..9060adcf7cf8 100644 > --- a/drivers/gpu/drm/drm_fb_helper.c > +++ b/drivers/gpu/drm/drm_fb_helper.c > @@ -119,6 +119,7 @@ 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)); mode_config.mutex isn't needed anymore here (with the recommendations at the bottom), please remove. > > count = fb_helper->connector_count + 1; > @@ -141,6 +142,7 @@ static int __drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, > drm_connector_get(connector); > conn->connector = connector; > fb_helper->connector_info[fb_helper->connector_count++] = conn; > + > return 0; > } > > @@ -149,11 +151,13 @@ 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); Same. > > 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; > } > @@ -183,6 +187,7 @@ 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); Same. > drm_connector_list_iter_begin(dev, &conn_iter); > drm_for_each_connector_iter(connector, &conn_iter) { > @@ -206,6 +211,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper) > out: > drm_connector_list_iter_end(&conn_iter); > mutex_unlock(&dev->mode_config.mutex); > + mutex_unlock(&fb_helper->lock); > > return ret; > } > @@ -220,6 +226,7 @@ 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)); Same. > > for (i = 0; i < fb_helper->connector_count; i++) { > @@ -246,11 +253,13 @@ 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; > } > @@ -502,16 +511,21 @@ 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); > @@ -747,6 +761,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper, > INIT_WORK(&helper->resume_work, drm_fb_helper_resume_worker); > 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; > } > @@ -912,6 +927,7 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper) > } > mutex_unlock(&kernel_fb_helper_lock); > > + mutex_destroy(&fb_helper->lock); > drm_fb_helper_crtc_free(fb_helper); > > } > @@ -2421,25 +2437,34 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config); > int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper) > { > struct drm_device *dev = fb_helper->dev; > + int err = 0; > > if (!drm_fbdev_emulation) > return 0; > > + mutex_lock(&fb_helper->lock); > mutex_lock(&dev->mode_config.mutex); > + > if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) { > fb_helper->delayed_hotplug = true; > mutex_unlock(&dev->mode_config.mutex); > - return 0; > + goto unlock; > } > + > DRM_DEBUG_KMS("\n"); > > drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height); > > mutex_unlock(&dev->mode_config.mutex); > + mutex_unlock(&fb_helper->lock); > > 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 119e5e4609c7..33771d0c44e3 100644 > --- a/include/drm/drm_fb_helper.h > +++ b/include/drm/drm_fb_helper.h > @@ -201,6 +201,13 @@ struct drm_fb_helper { > struct work_struct resume_work; > > /** > + * @lock: > + * > + * Top-level FB helper lock. Bit more detail would be good here. "This protects all the internal data structures and lists, like @connector_info or @crtc_info." > + */ > + struct mutex lock; > + > + /** > * @kernel_fb_list: > * > * Entry on the global kernel_fb_helper_list, used for kgdb entry/exit. So I think you're missing to protect almost all the fbdev paths. Essentially anything looking at crtc_info or connector_info must hold the new lock, which means all the places that currently call drm_modeset_lock_all() need to grab this new lock too. Best way to make sure you catch them all is to also update the lockdep assert in drm_fb_helper_for_each_connector(). There's still a massive mess going with locking here, especially around the probe code and drm_fb_helper_is_bound, but that's a different thing and better left for cleanup later on. -Daniel
On Tue, Mar 21, 2017 at 11:00:23AM +0100, Daniel Vetter wrote: > On Tue, Mar 21, 2017 at 09:13:53AM +0100, Thierry Reding wrote: > > From: Thierry Reding <treding@nvidia.com> > > > > 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. > > > > Tested-by: John Stultz <john.stultz@linaro.org> > > Signed-off-by: Thierry Reding <treding@nvidia.com> > > Some suggestions below, since I think this state of locking implemented > here is a bit a too awkwared intermediate thing. To clarify: After having reviewed the next patch I think this here is fine. So gets an Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch> as-is. I just think we want a notch more here. But if you're burried too much we can do that as a follow-up too, but in that case please add a FIXME to e.g. the @lock kernel-doc: "FIXME: fbdev emulation locking is a mess, long term we want to protect all helper internal state with this lock, and reduce core KMS locking as much as possible." Your choice :-) Cheers, Daniel > > > --- > > drivers/gpu/drm/drm_fb_helper.c | 27 ++++++++++++++++++++++++++- > > include/drm/drm_fb_helper.h | 7 +++++++ > > 2 files changed, 33 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c > > index 6af80afc4f40..9060adcf7cf8 100644 > > --- a/drivers/gpu/drm/drm_fb_helper.c > > +++ b/drivers/gpu/drm/drm_fb_helper.c > > @@ -119,6 +119,7 @@ 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)); > > mode_config.mutex isn't needed anymore here (with the recommendations at > the bottom), please remove. > > > > count = fb_helper->connector_count + 1; > > @@ -141,6 +142,7 @@ static int __drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, > > drm_connector_get(connector); > > conn->connector = connector; > > fb_helper->connector_info[fb_helper->connector_count++] = conn; > > + > > return 0; > > } > > > > @@ -149,11 +151,13 @@ 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); > > Same. > > > > > 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; > > } > > @@ -183,6 +187,7 @@ 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); > > Same. > > > drm_connector_list_iter_begin(dev, &conn_iter); > > drm_for_each_connector_iter(connector, &conn_iter) { > > @@ -206,6 +211,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper) > > out: > > drm_connector_list_iter_end(&conn_iter); > > mutex_unlock(&dev->mode_config.mutex); > > + mutex_unlock(&fb_helper->lock); > > > > return ret; > > } > > @@ -220,6 +226,7 @@ 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)); > > Same. > > > > > for (i = 0; i < fb_helper->connector_count; i++) { > > @@ -246,11 +253,13 @@ 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; > > } > > @@ -502,16 +511,21 @@ 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); > > @@ -747,6 +761,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper, > > INIT_WORK(&helper->resume_work, drm_fb_helper_resume_worker); > > 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; > > } > > @@ -912,6 +927,7 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper) > > } > > mutex_unlock(&kernel_fb_helper_lock); > > > > + mutex_destroy(&fb_helper->lock); > > drm_fb_helper_crtc_free(fb_helper); > > > > } > > @@ -2421,25 +2437,34 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config); > > int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper) > > { > > struct drm_device *dev = fb_helper->dev; > > + int err = 0; > > > > if (!drm_fbdev_emulation) > > return 0; > > > > + mutex_lock(&fb_helper->lock); > > mutex_lock(&dev->mode_config.mutex); > > + > > if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) { > > fb_helper->delayed_hotplug = true; > > mutex_unlock(&dev->mode_config.mutex); > > - return 0; > > + goto unlock; > > } > > + > > DRM_DEBUG_KMS("\n"); > > > > drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height); > > > > mutex_unlock(&dev->mode_config.mutex); > > + mutex_unlock(&fb_helper->lock); > > > > 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 119e5e4609c7..33771d0c44e3 100644 > > --- a/include/drm/drm_fb_helper.h > > +++ b/include/drm/drm_fb_helper.h > > @@ -201,6 +201,13 @@ struct drm_fb_helper { > > struct work_struct resume_work; > > > > /** > > + * @lock: > > + * > > + * Top-level FB helper lock. > > Bit more detail would be good here. > > "This protects all the internal data structures and lists, like > @connector_info or @crtc_info." > > > + */ > > + struct mutex lock; > > + > > + /** > > * @kernel_fb_list: > > * > > * Entry on the global kernel_fb_helper_list, used for kgdb entry/exit. > > So I think you're missing to protect almost all the fbdev paths. > Essentially anything looking at crtc_info or connector_info must hold the > new lock, which means all the places that currently call > drm_modeset_lock_all() need to grab this new lock too. > > Best way to make sure you catch them all is to also update the lockdep > assert in drm_fb_helper_for_each_connector(). > > There's still a massive mess going with locking here, especially around > the probe code and drm_fb_helper_is_bound, but that's a different thing > and better left for cleanup later on. > -Daniel > -- > Daniel Vetter > Software Engineer, Intel Corporation > http://blog.ffwll.ch
diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 6af80afc4f40..9060adcf7cf8 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -119,6 +119,7 @@ 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; @@ -141,6 +142,7 @@ static int __drm_fb_helper_add_one_connector(struct drm_fb_helper *fb_helper, drm_connector_get(connector); conn->connector = connector; fb_helper->connector_info[fb_helper->connector_count++] = conn; + return 0; } @@ -149,11 +151,13 @@ 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; } @@ -183,6 +187,7 @@ 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_connector_list_iter_begin(dev, &conn_iter); drm_for_each_connector_iter(connector, &conn_iter) { @@ -206,6 +211,7 @@ int drm_fb_helper_single_add_all_connectors(struct drm_fb_helper *fb_helper) out: drm_connector_list_iter_end(&conn_iter); mutex_unlock(&dev->mode_config.mutex); + mutex_unlock(&fb_helper->lock); return ret; } @@ -220,6 +226,7 @@ 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++) { @@ -246,11 +253,13 @@ 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; } @@ -502,16 +511,21 @@ 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); @@ -747,6 +761,7 @@ void drm_fb_helper_prepare(struct drm_device *dev, struct drm_fb_helper *helper, INIT_WORK(&helper->resume_work, drm_fb_helper_resume_worker); 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; } @@ -912,6 +927,7 @@ void drm_fb_helper_fini(struct drm_fb_helper *fb_helper) } mutex_unlock(&kernel_fb_helper_lock); + mutex_destroy(&fb_helper->lock); drm_fb_helper_crtc_free(fb_helper); } @@ -2421,25 +2437,34 @@ EXPORT_SYMBOL(drm_fb_helper_initial_config); int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper) { struct drm_device *dev = fb_helper->dev; + int err = 0; if (!drm_fbdev_emulation) return 0; + mutex_lock(&fb_helper->lock); mutex_lock(&dev->mode_config.mutex); + if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) { fb_helper->delayed_hotplug = true; mutex_unlock(&dev->mode_config.mutex); - return 0; + goto unlock; } + DRM_DEBUG_KMS("\n"); drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height); mutex_unlock(&dev->mode_config.mutex); + mutex_unlock(&fb_helper->lock); 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 119e5e4609c7..33771d0c44e3 100644 --- a/include/drm/drm_fb_helper.h +++ b/include/drm/drm_fb_helper.h @@ -201,6 +201,13 @@ struct drm_fb_helper { struct work_struct resume_work; /** + * @lock: + * + * Top-level FB helper lock. + */ + struct mutex lock; + + /** * @kernel_fb_list: * * Entry on the global kernel_fb_helper_list, used for kgdb entry/exit.