[PATCH] drm: vc4: Fix race during binding

[Stefan Wahren]

This fixes the race between vc4_overflow_mem_work and the init of the
job lock. Otherwise we could trigger a NULL pointer dereference
during VC4 binding.

Link: https://github.com/anholt/linux/issues/114
Signed-off-by: Stefan Wahren <stefan.wahren at i2se.com>
Fixes: d5b1a78a772f ("drm/vc4: Add support for drawing 3D frames.")
---
 drivers/gpu/drm/vc4/vc4_gem.c | 1 -
 drivers/gpu/drm/vc4/vc4_irq.c | 1 +
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vc4/vc4_gem.c b/drivers/gpu/drm/vc4/vc4_gem.c
index d0c6bfb..47d964f 100644
--- a/drivers/gpu/drm/vc4/vc4_gem.c
+++ b/drivers/gpu/drm/vc4/vc4_gem.c
@@ -1088,7 +1088,6 @@ vc4_gem_init(struct drm_device *dev)
 	INIT_LIST_HEAD(&vc4->render_job_list);
 	INIT_LIST_HEAD(&vc4->job_done_list);
 	INIT_LIST_HEAD(&vc4->seqno_cb_list);
-	spin_lock_init(&vc4->job_lock);
 
 	INIT_WORK(&vc4->hangcheck.reset_work, vc4_reset_work);
 	setup_timer(&vc4->hangcheck.timer,
diff --git a/drivers/gpu/drm/vc4/vc4_irq.c b/drivers/gpu/drm/vc4/vc4_irq.c
index 7d7af3a..d508d13 100644
--- a/drivers/gpu/drm/vc4/vc4_irq.c
+++ b/drivers/gpu/drm/vc4/vc4_irq.c
@@ -195,6 +195,7 @@ vc4_irq_preinstall(struct drm_device *dev)
 	struct vc4_dev *vc4 = to_vc4_dev(dev);
 
 	init_waitqueue_head(&vc4->job_wait_queue);
+	spin_lock_init(&vc4->job_lock);
 	INIT_WORK(&vc4->overflow_mem_work, vc4_overflow_mem_work);
 
 	/* Clear any pending interrupts someone might have left around
-- 
2.7.4