drm_vblank_off() requires callers to hold the event_lock, while itself
locking vbl_time and vblank_time_lock. This defines a dependency chain
that conflicts with the one in drm_handle_vblank() where we first lock
vblank_time_lock and then the event_lock. Fix this by reversing the
locking order in drm_handle_vblank().
This should've triggered a lockdep warning in the exynos driver, the
rest of the drivers were ok, since they are not using drm_vblank_off(),
or as in the case of the intel driver were not holding the event_lock
when calling drm_vblank_off(). This latter issue is addressed in the
next patch.
Signed-off-by: Imre Deak <imre.deak@xxxxxxxxx>
---
drivers/gpu/drm/drm_irq.c | 32 ++++++++++++++++++++------------
1 file changed, 20 insertions(+), 12 deletions(-)
Tested with i915, the rest of the drivers should be checked with
lockdep enabled.
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 3a3d0ce..2193d4a 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -1236,17 +1236,21 @@ done:
return ret;
}
+/**
+ * drm_handle_vblank_events - send pending vblank events
+ * @dev: DRM device
+ * @crtc: crtc where the vblank(s) happened
+ *
+ * Must be called with @dev->event_lock held.
+ */
static void drm_handle_vblank_events(struct drm_device *dev, int crtc)
{
struct drm_pending_vblank_event *e, *t;
struct timeval now;
- unsigned long flags;
unsigned int seq;
seq = drm_vblank_count_and_time(dev, crtc, &now);
- spin_lock_irqsave(&dev->event_lock, flags);
-
list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
if (e->pipe != crtc)
continue;
@@ -1266,8 +1270,6 @@ static void drm_handle_vblank_events(struct drm_device *dev, int crtc)
e->event.sequence);
}
- spin_unlock_irqrestore(&dev->event_lock, flags);
-
trace_drm_vblank_event(crtc, seq);
}
@@ -1285,21 +1287,22 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc)
s64 diff_ns;
struct timeval tvblank;
unsigned long irqflags;
+ bool ret = false;
if (!dev->num_crtcs)
return false;
+ spin_lock_irqsave(&dev->event_lock, irqflags);
+
/* Need timestamp lock to prevent concurrent execution with
* vblank enable/disable, as this would cause inconsistent
* or corrupted timestamps and vblank counts.
*/
- spin_lock_irqsave(&dev->vblank_time_lock, irqflags);
+ spin_lock(&dev->vblank_time_lock);
/* Vblank irq handling disabled. Nothing to do. */
- if (!dev->vblank_enabled[crtc]) {
- spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
- return false;
- }
+ if (!dev->vblank_enabled[crtc])
+ goto unlock_ret;
/* Fetch corresponding timestamp for this vblank interval from
* driver and store it in proper slot of timestamp ringbuffer.
@@ -1340,7 +1343,12 @@ bool drm_handle_vblank(struct drm_device *dev, int crtc)
DRM_WAKEUP(&dev->vbl_queue[crtc]);
drm_handle_vblank_events(dev, crtc);
- spin_unlock_irqrestore(&dev->vblank_time_lock, irqflags);
- return true;
+ ret = true;
+
+unlock_ret:
+ spin_unlock(&dev->vblank_time_lock);
+ spin_unlock_irqrestore(&dev->event_lock, irqflags);
+
+ return ret;
}
EXPORT_SYMBOL(drm_handle_vblank);
--
1.7.9.5
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