drm/nouveau: Refactor context destruction to avoid a lock ordering issue.
The destroy_context() engine hooks call gpuobj management functions to
release the channel resources, these functions use HARDIRQ-unsafe locks
whereas destroy_context() is called with the HARDIRQ-safe
context_switch_lock held, that's a lock ordering violation.
Push the engine-specific channel destruction logic into destroy_context()
and let the hardware-specific code lock and unlock when it's actually
needed. Change the engine destruction order to avoid a race in the small
gap between pgraph and pfifo context uninitialization.
Reported-by: Marcin Slusarz <marcin.slusarz@gmail.com>
Signed-off-by: Francisco Jerez <currojerez@riseup.net>
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/nouveau_channel.c b/drivers/gpu/drm/nouveau/nouveau_channel.c
index 0e2414b..9a051fa 100644
--- a/drivers/gpu/drm/nouveau/nouveau_channel.c
+++ b/drivers/gpu/drm/nouveau/nouveau_channel.c
@@ -313,32 +313,20 @@
/* boot it off the hardware */
pfifo->reassign(dev, false);
- /* We want to give pgraph a chance to idle and get rid of all potential
- * errors. We need to do this before the lock, otherwise the irq handler
- * is unable to process them.
+ /* We want to give pgraph a chance to idle and get rid of all
+ * potential errors. We need to do this without the context
+ * switch lock held, otherwise the irq handler is unable to
+ * process them.
*/
if (pgraph->channel(dev) == chan)
nouveau_wait_for_idle(dev);
- spin_lock_irqsave(&dev_priv->context_switch_lock, flags);
-
- pgraph->fifo_access(dev, false);
- if (pgraph->channel(dev) == chan)
- pgraph->unload_context(dev);
- pgraph->destroy_context(chan);
- pgraph->fifo_access(dev, true);
-
- if (pfifo->channel_id(dev) == chan->id) {
- pfifo->disable(dev);
- pfifo->unload_context(dev);
- pfifo->enable(dev);
- }
+ /* destroy the engine specific contexts */
pfifo->destroy_context(chan);
+ pgraph->destroy_context(chan);
pfifo->reassign(dev, true);
- spin_unlock_irqrestore(&dev_priv->context_switch_lock, flags);
-
/* aside from its resources, the channel should now be dead,
* remove it from the channel list
*/