drm/i915: Track the previous pinned context inside the request
As the contexts are accessed by the hardware until the switch is completed
to a new context, the hardware may still be writing to the context object
after the breadcrumb is visible. We must not unpin/unbind/prune that
object whilst still active and so we keep the previous context pinned until
the following request. We can generalise the tracking we already do via
the engine->last_context and move it to the request so that it works
equally for execlists and GuC.
v2: Drop the execlists double pin as that exposes a race inside the lrc
irq handler as it tries to access the context after it may be retired.
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>
Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1461833819-3991-22-git-send-email-chris@chris-wilson.co.uk
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index e9bf45a..72cd084 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1413,13 +1413,13 @@
list_del_init(&request->list);
i915_gem_request_remove_from_client(request);
- if (request->ctx) {
+ if (request->previous_context) {
if (i915.enable_execlists)
- intel_lr_context_unpin(request->ctx, request->engine);
-
- i915_gem_context_unreference(request->ctx);
+ intel_lr_context_unpin(request->previous_context,
+ request->engine);
}
+ i915_gem_context_unreference(request->ctx);
i915_gem_request_unreference(request);
}