drm/i915/gem: Don't leak non-persistent requests on changing engines

If we have a set of active engines marked as being non-persistent, we
lose track of those if the user replaces those engines with
I915_CONTEXT_PARAM_ENGINES. As part of our uABI contract is that
non-persistent requests are terminated if they are no longer being
tracked by the user's context (in order to prevent a lost request
causing an untracked and so unstoppable GPU hang), we need to apply the
same context cancellation upon changing engines.

v2: Track stale engines[] so we only reap at context closure.
v3: Tvrtko spotted races with closing contexts and set-engines, so add a
veneer of kill-everything paranoia to clean up after losing a race.

Fixes: a0e047156cde ("drm/i915/gem: Make context persistence optional")
Testcase: igt/gem_ctx_peristence/replace
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200211144831.1011498-1-chris@chris-wilson.co.uk

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
index 017ca803ab47..b9a1d54a4643 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context_types.h
@@ -20,6 +20,7 @@
 #include "gt/intel_context_types.h"
 
 #include "i915_scheduler.h"
+#include "i915_sw_fence.h"
 
 struct pid;
 
@@ -30,7 +31,12 @@ struct intel_timeline;
 struct intel_ring;
 
 struct i915_gem_engines {
-	struct rcu_head rcu;
+	union {
+		struct list_head link;
+		struct rcu_head rcu;
+	};
+	struct i915_sw_fence fence;
+	struct i915_gem_context *ctx;
 	unsigned int num_engines;
 	struct intel_context *engines[];
 };
@@ -173,6 +179,11 @@ struct i915_gem_context {
 	 * context in messages.
 	 */
 	char name[TASK_COMM_LEN + 8];
+
+	struct {
+		struct spinlock lock;
+		struct list_head engines;
+	} stale;
 };
 
 #endif /* __I915_GEM_CONTEXT_TYPES_H__ */