From: Daniel Vetter daniel.vetter@ffwll.ch
commit f54b3ca7ea1e5e02f481cf4ca54568e57bd66086 upstream.
This reverts commit 1815d9c86e3090477fbde066ff314a7e9721ee0f.
Unfortunately this inverts the locking hierarchy, so back to the drawing board. Full lockdep splat below:
====================================================== WARNING: possible circular locking dependency detected 5.13.0-rc7-CI-CI_DRM_10254+ #1 Not tainted ------------------------------------------------------ kms_frontbuffer/1087 is trying to acquire lock: ffff88810dcd01a8 (&dev->master_mutex){+.+.}-{3:3}, at: drm_is_current_master+0x1b/0x40 but task is already holding lock: ffff88810dcd0488 (&dev->mode_config.mutex){+.+.}-{3:3}, at: drm_mode_getconnector+0x1c6/0x4a0 which lock already depends on the new lock. the existing dependency chain (in reverse order) is: -> #2 (&dev->mode_config.mutex){+.+.}-{3:3}: __mutex_lock+0xab/0x970 drm_client_modeset_probe+0x22e/0xca0 __drm_fb_helper_initial_config_and_unlock+0x42/0x540 intel_fbdev_initial_config+0xf/0x20 [i915] async_run_entry_fn+0x28/0x130 process_one_work+0x26d/0x5c0 worker_thread+0x37/0x380 kthread+0x144/0x170 ret_from_fork+0x1f/0x30 -> #1 (&client->modeset_mutex){+.+.}-{3:3}: __mutex_lock+0xab/0x970 drm_client_modeset_commit_locked+0x1c/0x180 drm_client_modeset_commit+0x1c/0x40 __drm_fb_helper_restore_fbdev_mode_unlocked+0x88/0xb0 drm_fb_helper_set_par+0x34/0x40 intel_fbdev_set_par+0x11/0x40 [i915] fbcon_init+0x270/0x4f0 visual_init+0xc6/0x130 do_bind_con_driver+0x1e5/0x2d0 do_take_over_console+0x10e/0x180 do_fbcon_takeover+0x53/0xb0 register_framebuffer+0x22d/0x310 __drm_fb_helper_initial_config_and_unlock+0x36c/0x540 intel_fbdev_initial_config+0xf/0x20 [i915] async_run_entry_fn+0x28/0x130 process_one_work+0x26d/0x5c0 worker_thread+0x37/0x380 kthread+0x144/0x170 ret_from_fork+0x1f/0x30 -> #0 (&dev->master_mutex){+.+.}-{3:3}: __lock_acquire+0x151e/0x2590 lock_acquire+0xd1/0x3d0 __mutex_lock+0xab/0x970 drm_is_current_master+0x1b/0x40 drm_mode_getconnector+0x37e/0x4a0 drm_ioctl_kernel+0xa8/0xf0 drm_ioctl+0x1e8/0x390 __x64_sys_ioctl+0x6a/0xa0 do_syscall_64+0x39/0xb0 entry_SYSCALL_64_after_hwframe+0x44/0xae other info that might help us debug this: Chain exists of: &dev->master_mutex --> &client->modeset_mutex --> &dev->mode_config.mutex Possible unsafe locking scenario: CPU0 CPU1 ---- ---- lock(&dev->mode_config.mutex); lock(&client->modeset_mutex); lock(&dev->mode_config.mutex); lock(&dev->master_mutex); --- drivers/gpu/drm/drm_auth.c | 51 ++++++++++++++------------------------ 1 file changed, 19 insertions(+), 32 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 86d4b72e95cb..232abbba3686 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -61,35 +61,6 @@ * trusted clients. */
-static bool drm_is_current_master_locked(struct drm_file *fpriv) -{ - lockdep_assert_held_once(&fpriv->master->dev->master_mutex); - - return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; -} - -/** - * drm_is_current_master - checks whether @priv is the current master - * @fpriv: DRM file private - * - * Checks whether @fpriv is current master on its device. This decides whether a - * client is allowed to run DRM_MASTER IOCTLs. - * - * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting - * - the current master is assumed to own the non-shareable display hardware. - */ -bool drm_is_current_master(struct drm_file *fpriv) -{ - bool ret; - - mutex_lock(&fpriv->master->dev->master_mutex); - ret = drm_is_current_master_locked(fpriv); - mutex_unlock(&fpriv->master->dev->master_mutex); - - return ret; -} -EXPORT_SYMBOL(drm_is_current_master); - int drm_getmagic(struct drm_device *dev, void *data, struct drm_file *file_priv) { struct drm_auth *auth = data; @@ -252,7 +223,7 @@ int drm_setmaster_ioctl(struct drm_device *dev, void *data, if (ret) goto out_unlock;
- if (drm_is_current_master_locked(file_priv)) + if (drm_is_current_master(file_priv)) goto out_unlock;
if (dev->master) { @@ -301,7 +272,7 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, if (ret) goto out_unlock;
- if (!drm_is_current_master_locked(file_priv)) { + if (!drm_is_current_master(file_priv)) { ret = -EINVAL; goto out_unlock; } @@ -350,7 +321,7 @@ void drm_master_release(struct drm_file *file_priv) if (file_priv->magic) idr_remove(&file_priv->master->magic_map, file_priv->magic);
- if (!drm_is_current_master_locked(file_priv)) + if (!drm_is_current_master(file_priv)) goto out;
drm_legacy_lock_master_cleanup(dev, master); @@ -371,6 +342,22 @@ out: mutex_unlock(&dev->master_mutex); }
+/** + * drm_is_current_master - checks whether @priv is the current master + * @fpriv: DRM file private + * + * Checks whether @fpriv is current master on its device. This decides whether a + * client is allowed to run DRM_MASTER IOCTLs. + * + * Most of the modern IOCTL which require DRM_MASTER are for kernel modesetting + * - the current master is assumed to own the non-shareable display hardware. + */ +bool drm_is_current_master(struct drm_file *fpriv) +{ + return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master; +} +EXPORT_SYMBOL(drm_is_current_master); + /** * drm_master_get - reference a master pointer * @master: &struct drm_master