diff options
authorDaniel Vetter <>2013-12-10 13:20:59 +0100
committerDaniel Vetter <>2013-12-11 14:25:58 +0100
commit6c719faca2aceca72f1bf5b1645c1734ed3e9447 (patch)
parentad071acb53110c8efd26ff1e5b5d57449b43833b (diff)
drm/i915: don't update the dri1 breadcrumb with modesettingdrm-intel-fixes-2013-12-11
The update is horribly racy since it doesn't protect at all against concurrent closing of the master fd. And it can't really since that requires us to grab a mutex. Instead of jumping through hoops and offloading this to a worker thread just block this bit of code for the modesetting driver. Note that the race is fairly easy to hit since we call the breadcrumb function for any interrupt. So the vblank interrupt (which usually keeps going for a bit) is enough. But even if we'd block this and only update the breadcrumb for user interrupts from the CS we could hit this race with kms/gem userspace: If a non-master is waiting somewhere (and hence has interrupts enabled) and the master closes its fd (probably due to crashing). v2: Add a code comment to explain why fixing this for real isn't really worth it. Also improve the commit message a bit. v3: Fix the spelling in the comment. Reported-by: Eugene Shatokhin <> Cc: Eugene Shatokhin <> Cc: Acked-by: Chris Wilson <> Tested-by: Eugene Shatokhin <> Signed-off-by: Daniel Vetter <>
1 files changed, 8 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 197db0993a2..5c648425c1e 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -83,6 +83,14 @@ void i915_update_dri1_breadcrumb(struct drm_device *dev)
drm_i915_private_t *dev_priv = dev->dev_private;
struct drm_i915_master_private *master_priv;
+ /*
+ * The dri breadcrumb update races against the drm master disappearing.
+ * Instead of trying to fix this (this is by far not the only ums issue)
+ * just don't do the update in kms mode.
+ */
+ if (drm_core_check_feature(dev, DRIVER_MODESET))
+ return;
if (dev->primary->master) {
master_priv = dev->primary->master->driver_priv;
if (master_priv->sarea_priv)