drm_fb_helper_is_bound() is used to check if DRM userspace is in control. This is done by looking at the fb on the primary plane. By the time fb-helper gets around to committing, it's possible that the facts have changed.
Avoid this race by holding the drm_device->master_mutex lock while committing. When DRM userspace does its first open, it will now wait until fb-helper is done. The helper will stay away if there's a master.
Locking rule: Always take the fb-helper lock first.
v2: - Remove drm_fb_helper_is_bound() (Daniel Vetter) - No need to check fb_helper->dev->master in drm_fb_helper_single_fb_probe(), restore_fbdev_mode() has the check.
Suggested-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Noralf Trønnes noralf@tronnes.org Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch --- drivers/gpu/drm/drm_auth.c | 20 ++++++++ drivers/gpu/drm/drm_fb_helper.c | 90 ++++++++++++++++----------------- drivers/gpu/drm/drm_internal.h | 2 + 3 files changed, 67 insertions(+), 45 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 1669c42c40ed..db199807b7dc 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -368,3 +368,23 @@ void drm_master_put(struct drm_master **master) *master = NULL; } EXPORT_SYMBOL(drm_master_put); + +/* Used by drm_client and drm_fb_helper */ +bool drm_master_internal_acquire(struct drm_device *dev) +{ + mutex_lock(&dev->master_mutex); + if (dev->master) { + mutex_unlock(&dev->master_mutex); + return false; + } + + return true; +} +EXPORT_SYMBOL(drm_master_internal_acquire); + +/* Used by drm_client and drm_fb_helper */ +void drm_master_internal_release(struct drm_device *dev) +{ + mutex_unlock(&dev->master_mutex); +} +EXPORT_SYMBOL(drm_master_internal_release); diff --git a/drivers/gpu/drm/drm_fb_helper.c b/drivers/gpu/drm/drm_fb_helper.c index 2339f0f8f5a8..578428461391 100644 --- a/drivers/gpu/drm/drm_fb_helper.c +++ b/drivers/gpu/drm/drm_fb_helper.c @@ -44,6 +44,7 @@
#include "drm_crtc_internal.h" #include "drm_crtc_helper_internal.h" +#include "drm_internal.h"
static bool drm_fbdev_emulation = true; module_param_named(fbdev_emulation, drm_fbdev_emulation, bool, 0600); @@ -509,7 +510,7 @@ static int restore_fbdev_mode_legacy(struct drm_fb_helper *fb_helper) return ret; }
-static int restore_fbdev_mode(struct drm_fb_helper *fb_helper) +static int restore_fbdev_mode_force(struct drm_fb_helper *fb_helper) { struct drm_device *dev = fb_helper->dev;
@@ -519,6 +520,21 @@ static int restore_fbdev_mode(struct drm_fb_helper *fb_helper) return restore_fbdev_mode_legacy(fb_helper); }
+static int restore_fbdev_mode(struct drm_fb_helper *fb_helper) +{ + struct drm_device *dev = fb_helper->dev; + int ret; + + if (!drm_master_internal_acquire(dev)) + return -EBUSY; + + ret = restore_fbdev_mode_force(fb_helper); + + drm_master_internal_release(dev); + + return ret; +} + /** * drm_fb_helper_restore_fbdev_mode_unlocked - restore fbdev configuration * @fb_helper: driver-allocated fbdev helper, can be NULL @@ -556,34 +572,6 @@ int drm_fb_helper_restore_fbdev_mode_unlocked(struct drm_fb_helper *fb_helper) } EXPORT_SYMBOL(drm_fb_helper_restore_fbdev_mode_unlocked);
-static bool drm_fb_helper_is_bound(struct drm_fb_helper *fb_helper) -{ - struct drm_device *dev = fb_helper->dev; - struct drm_crtc *crtc; - int bound = 0, crtcs_bound = 0; - - /* - * Sometimes user space wants everything disabled, so don't steal the - * display if there's a master. - */ - if (READ_ONCE(dev->master)) - return false; - - drm_for_each_crtc(crtc, dev) { - drm_modeset_lock(&crtc->mutex, NULL); - if (crtc->primary->fb) - crtcs_bound++; - if (crtc->primary->fb == fb_helper->fb) - bound++; - drm_modeset_unlock(&crtc->mutex); - } - - if (bound < crtcs_bound) - return false; - - return true; -} - #ifdef CONFIG_MAGIC_SYSRQ /* * restore fbcon display for all kms driver's using this helper, used for sysrq @@ -604,7 +592,7 @@ static bool drm_fb_helper_force_kernel_mode(void) continue;
mutex_lock(&helper->lock); - ret = restore_fbdev_mode(helper); + ret = restore_fbdev_mode_force(helper); if (ret) error = true; mutex_unlock(&helper->lock); @@ -663,20 +651,22 @@ static void dpms_legacy(struct drm_fb_helper *fb_helper, int dpms_mode) static void drm_fb_helper_dpms(struct fb_info *info, int dpms_mode) { struct drm_fb_helper *fb_helper = info->par; + struct drm_device *dev = fb_helper->dev;
/* * For each CRTC in this fb, turn the connectors on/off. */ mutex_lock(&fb_helper->lock); - if (!drm_fb_helper_is_bound(fb_helper)) { - mutex_unlock(&fb_helper->lock); - return; - } + if (!drm_master_internal_acquire(dev)) + goto unlock;
- if (drm_drv_uses_atomic_modeset(fb_helper->dev)) + if (drm_drv_uses_atomic_modeset(dev)) restore_fbdev_mode_atomic(fb_helper, dpms_mode == DRM_MODE_DPMS_ON); else dpms_legacy(fb_helper, dpms_mode); + + drm_master_internal_release(dev); +unlock: mutex_unlock(&fb_helper->lock); }
@@ -1509,6 +1499,7 @@ static int setcmap_atomic(struct fb_cmap *cmap, struct fb_info *info) int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info) { struct drm_fb_helper *fb_helper = info->par; + struct drm_device *dev = fb_helper->dev; int ret;
if (oops_in_progress) @@ -1516,9 +1507,9 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info)
mutex_lock(&fb_helper->lock);
- if (!drm_fb_helper_is_bound(fb_helper)) { + if (!drm_master_internal_acquire(dev)) { ret = -EBUSY; - goto out; + goto unlock; }
if (info->fix.visual == FB_VISUAL_TRUECOLOR) @@ -1528,7 +1519,8 @@ int drm_fb_helper_setcmap(struct fb_cmap *cmap, struct fb_info *info) else ret = setcmap_legacy(cmap, info);
-out: + drm_master_internal_release(dev); +unlock: mutex_unlock(&fb_helper->lock);
return ret; @@ -1548,12 +1540,13 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd, unsigned long arg) { struct drm_fb_helper *fb_helper = info->par; + struct drm_device *dev = fb_helper->dev; struct drm_mode_set *mode_set; struct drm_crtc *crtc; int ret = 0;
mutex_lock(&fb_helper->lock); - if (!drm_fb_helper_is_bound(fb_helper)) { + if (!drm_master_internal_acquire(dev)) { ret = -EBUSY; goto unlock; } @@ -1591,11 +1584,12 @@ int drm_fb_helper_ioctl(struct fb_info *info, unsigned int cmd, }
ret = 0; - goto unlock; + break; default: ret = -ENOTTY; }
+ drm_master_internal_release(dev); unlock: mutex_unlock(&fb_helper->lock); return ret; @@ -1847,15 +1841,18 @@ int drm_fb_helper_pan_display(struct fb_var_screeninfo *var, return -EBUSY;
mutex_lock(&fb_helper->lock); - if (!drm_fb_helper_is_bound(fb_helper)) { - mutex_unlock(&fb_helper->lock); - return -EBUSY; + if (!drm_master_internal_acquire(dev)) { + ret = -EBUSY; + goto unlock; }
if (drm_drv_uses_atomic_modeset(dev)) ret = pan_display_atomic(var, info); else ret = pan_display_legacy(var, info); + + drm_master_internal_release(dev); +unlock: mutex_unlock(&fb_helper->lock);
return ret; @@ -2014,7 +2011,7 @@ static int drm_fb_helper_single_fb_probe(struct drm_fb_helper *fb_helper, DRM_INFO("Cannot find any crtc or sizes\n");
/* First time: disable all crtc's.. */ - if (!fb_helper->deferred_setup && !READ_ONCE(fb_helper->dev->master)) + if (!fb_helper->deferred_setup) restore_fbdev_mode(fb_helper); return -EAGAIN; } @@ -3028,6 +3025,7 @@ 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 || !fb_helper) @@ -3040,12 +3038,14 @@ int drm_fb_helper_hotplug_event(struct drm_fb_helper *fb_helper) return err; }
- if (!fb_helper->fb || !drm_fb_helper_is_bound(fb_helper)) { + if (!fb_helper->fb || !drm_master_internal_acquire(dev)) { fb_helper->delayed_hotplug = true; mutex_unlock(&fb_helper->lock); return err; }
+ drm_master_internal_release(dev); + DRM_DEBUG_KMS("\n");
drm_setup_crtcs(fb_helper, fb_helper->fb->width, fb_helper->fb->height); diff --git a/drivers/gpu/drm/drm_internal.h b/drivers/gpu/drm/drm_internal.h index d9a483a5fce0..3ee97c9998a2 100644 --- a/drivers/gpu/drm/drm_internal.h +++ b/drivers/gpu/drm/drm_internal.h @@ -91,6 +91,8 @@ int drm_dropmaster_ioctl(struct drm_device *dev, void *data, struct drm_file *file_priv); int drm_master_open(struct drm_file *file_priv); void drm_master_release(struct drm_file *file_priv); +bool drm_master_internal_acquire(struct drm_device *dev); +void drm_master_internal_release(struct drm_device *dev);
/* drm_sysfs.c */ extern struct class *drm_class;