On 20/11/2019 15:21, Chris Wilson wrote:
Since retirement may be running in a worker on another CPU, it may be
skipped in the local intel_gt_wait_for_idle(). To ensure the state is
consistent for our sanity checks upon load, serialise with the remote
retirer by waiting on the timeline->mutex.
What may get skipped? Timeline might have been removed from the active
list before wait_for_idle? But why would that be bad for this code? It
just splits part of the retirement to two paths - wait_for_idle still...
oops wait.. indeed.. wait_for_idle used to guarantee retirement and now
it can be ongoing. Does wait_for_idle needs to always wait or you think
case-by-case basis is better?
Regards,
Tvrtko
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_gem.c | 26 +++++++++++++++++++++++---
1 file changed, 23 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1ba5f26700b0..61395b03443e 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -45,6 +45,7 @@
#include "gem/i915_gem_context.h"
#include "gem/i915_gem_ioctls.h"
#include "gem/i915_gem_pm.h"
+#include "gt/intel_context.h"
#include "gt/intel_engine_user.h"
#include "gt/intel_gt.h"
#include "gt/intel_gt_pm.h"
@@ -1041,6 +1042,18 @@ i915_gem_madvise_ioctl(struct drm_device *dev, void *data,
return err;
}
+static int __intel_context_flush_retire(struct intel_context *ce)
+{
+ struct intel_timeline *tl;
+
+ tl = intel_context_timeline_lock(ce);
+ if (IS_ERR(tl))
+ return PTR_ERR(tl);
+
+ intel_context_timeline_unlock(tl);
+ return 0;
+}
+
static int __intel_engines_record_defaults(struct intel_gt *gt)
{
struct i915_request *requests[I915_NUM_ENGINES] = {};
@@ -1109,13 +1122,20 @@ static int __intel_engines_record_defaults(struct intel_gt *gt)
if (!rq)
continue;
- /* We want to be able to unbind the state from the GGTT */
- GEM_BUG_ON(intel_context_is_pinned(rq->hw_context));
-
+ GEM_BUG_ON(!test_bit(CONTEXT_ALLOC_BIT,
+ &rq->hw_context->flags));
state = rq->hw_context->state;
if (!state)
continue;
+ /* Serialise with retirement on another CPU */
+ err = __intel_context_flush_retire(rq->hw_context);
+ if (err)
+ goto out;
+
+ /* We want to be able to unbind the state from the GGTT */
+ GEM_BUG_ON(intel_context_is_pinned(rq->hw_context));
+
/*
* As we will hold a reference to the logical state, it will
* not be torn down with the context, and importantly the
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