On 08/07/2019 12:39, Chris Wilson wrote:
Modifying a remote context requires careful serialisation with requests
on that context, and that serialisation requires us to take their
timeline->mutex. Make it so.
Note that while struct_mutex rules, we can't create more than one
request in parallel, but that age is soon coming to an end.
v2: Though it doesn't affect the current users, contexts may share
timelines so check if we already hold the right mutex.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
---
drivers/gpu/drm/i915/gem/i915_gem_context.c | 16 ++-------
drivers/gpu/drm/i915/gt/intel_context.c | 38 +++++++++++++++++++++
drivers/gpu/drm/i915/gt/intel_context.h | 3 ++
drivers/gpu/drm/i915/i915_perf.c | 7 +---
4 files changed, 44 insertions(+), 20 deletions(-)
diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c
index 1f0d10bb88c1..6000177472ee 100644
--- a/drivers/gpu/drm/i915/gem/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c
@@ -1192,20 +1192,8 @@ gen8_modify_rpcs(struct intel_context *ce, struct intel_sseu sseu)
if (IS_ERR(rq))
return PTR_ERR(rq);
- /* Queue this switch after all other activity by this context. */
- ret = i915_active_request_set(&ce->ring->timeline->last_request, rq);
- if (ret)
- goto out_add;
-
- /*
- * Guarantee context image and the timeline remains pinned until the
- * modifying request is retired by setting the ce activity tracker.
- *
- * But we only need to take one pin on the account of it. Or in other
- * words transfer the pinned ce object to tracked active request.
- */
- GEM_BUG_ON(i915_active_is_idle(&ce->active));
- ret = i915_active_ref(&ce->active, rq->fence.context, rq);
+ /* Serialise with the remote context */
+ ret = intel_context_prepare_remote_request(ce, rq);
if (ret)
goto out_add;
diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 1110fc8f657a..b1e2e4b60027 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -239,6 +239,44 @@ void intel_context_exit_engine(struct intel_context *ce)
intel_engine_pm_put(ce->engine);
}
+int intel_context_prepare_remote_request(struct intel_context *ce,
+ struct i915_request *rq)
+{
+ struct intel_timeline *tl = ce->ring->timeline;
+ int err;
+
+ /* Only suitable for use in remotely modifying this context */
+ GEM_BUG_ON(rq->hw_context == ce);
+
+ if (rq->timeline != tl) { /* beware timeline sharing */
+ err = mutex_lock_interruptible_nested(&tl->mutex,
+ SINGLE_DEPTH_NESTING);
Which caller is holding tl->mutex?
Regards,
Tvrtko
+ if (err)
+ return err;
+ }
+ lockdep_assert_held(&tl->mutex);
+
+ /* Queue this switch after all other activity by this context. */
+ err = i915_active_request_set(&tl->last_request, rq);
+ if (err)
+ goto unlock;
+
+ /*
+ * Guarantee context image and the timeline remains pinned until the
+ * modifying request is retired by setting the ce activity tracker.
+ *
+ * But we only need to take one pin on the account of it. Or in other
+ * words transfer the pinned ce object to tracked active request.
+ */
+ GEM_BUG_ON(i915_active_is_idle(&ce->active));
+ err = i915_active_ref(&ce->active, rq->fence.context, rq);
+
+unlock:
+ if (rq->timeline != tl)
+ mutex_unlock(&tl->mutex);
+ return err;
+}
+
struct i915_request *intel_context_create_request(struct intel_context *ce)
{
struct i915_request *rq;
diff --git a/drivers/gpu/drm/i915/gt/intel_context.h b/drivers/gpu/drm/i915/gt/intel_context.h
index 40cd8320fcc3..b41c610c2ce6 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.h
+++ b/drivers/gpu/drm/i915/gt/intel_context.h
@@ -139,6 +139,9 @@ static inline void intel_context_timeline_unlock(struct intel_context *ce)
mutex_unlock(&ce->ring->timeline->mutex);
}
+int intel_context_prepare_remote_request(struct intel_context *ce,
+ struct i915_request *rq);
+
struct i915_request *intel_context_create_request(struct intel_context *ce);
#endif /* __INTEL_CONTEXT_H__ */
diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c
index 25c34a0b521e..6f77014640b8 100644
--- a/drivers/gpu/drm/i915/i915_perf.c
+++ b/drivers/gpu/drm/i915/i915_perf.c
@@ -1762,12 +1762,7 @@ static int gen8_modify_context(struct intel_context *ce,
return PTR_ERR(rq);
/* Serialise with the remote context */
- err = i915_active_request_set(&ce->ring->timeline->last_request, rq);
- if (err)
- goto out_add;
-
- /* Keep the remote context alive until after we finish editing */
- err = i915_active_ref(&ce->active, rq->fence.context, rq);
+ err = intel_context_prepare_remote_request(ce, rq);
if (err)
goto out_add;
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