[PATCH 25/36] drm/omap: tiler: fix race condition with engine->async

[Tomi Valkeinen]

The tiler irq handler uses engine->async value, but the code that sets
engine->async and enables the interrupt does not have a barrier. This
may cause the irq handler to see the old value of engine->async, causing
memory corruption.

Reported-by: Harinarayan Bhatta <harinarayan at ti.com>
Signed-off-by: Tomi Valkeinen <tomi.valkeinen at ti.com>
---
 drivers/gpu/drm/omapdrm/omap_dmm_tiler.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c b/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
index f06243b3d3c0..a1a824db1dd6 100644
--- a/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
+++ b/drivers/gpu/drm/omapdrm/omap_dmm_tiler.c
@@ -273,6 +273,8 @@ static int dmm_txn_commit(struct dmm_txn *txn, bool wait)
 
 	/* mark whether it is async to denote list management in IRQ handler */
 	engine->async = wait ? false : true;
+	/* verify that the irq handler sees the 'async' value */
+	smp_mb();
 
 	/* kick reload */
 	writel(engine->refill_pa,
-- 
2.3.3