On 8/10/20 12:30 PM, Maarten Lankhorst wrote:
Instead of doing everything inside of pin_mutex, we move all pinning
outside. Because i915_active has its own reference counting and
pinning is also having the same issues vs mutexes, we make sure
everything is pinned first, so the pinning in i915_active only needs
to bump refcounts. This allows us to take pin refcounts correctly
all the time.
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gt/intel_context.c | 232 +++++++++++-------
drivers/gpu/drm/i915/gt/intel_context_types.h | 4 +-
drivers/gpu/drm/i915/gt/intel_lrc.c | 34 ++-
.../gpu/drm/i915/gt/intel_ring_submission.c | 13 +-
drivers/gpu/drm/i915/gt/mock_engine.c | 13 +-
5 files changed, 190 insertions(+), 106 deletions(-)
diff --git a/drivers/gpu/drm/i915/gt/intel_context.c b/drivers/gpu/drm/i915/gt/intel_context.c
index 52db2bde44a3..efe9a7a89ede 100644
--- a/drivers/gpu/drm/i915/gt/intel_context.c
+++ b/drivers/gpu/drm/i915/gt/intel_context.c
@@ -93,79 +93,6 @@ static void intel_context_active_release(struct intel_context *ce)
i915_active_release(&ce->active);
}
-int __intel_context_do_pin(struct intel_context *ce)
-{
- int err;
-
- if (unlikely(!test_bit(CONTEXT_ALLOC_BIT, &ce->flags))) {
- err = intel_context_alloc_state(ce);
- if (err)
- return err;
- }
-
- err = i915_active_acquire(&ce->active);
- if (err)
- return err;
-
- if (mutex_lock_interruptible(&ce->pin_mutex)) {
- err = -EINTR;
- goto out_release;
- }
-
- if (unlikely(intel_context_is_closed(ce))) {
- err = -ENOENT;
- goto out_unlock;
- }
-
- if (likely(!atomic_add_unless(&ce->pin_count, 1, 0))) {
- err = intel_context_active_acquire(ce);
- if (unlikely(err))
- goto out_unlock;
-
- err = ce->ops->pin(ce);
- if (unlikely(err))
- goto err_active;
-
- CE_TRACE(ce, "pin ring:{start:%08x, head:%04x, tail:%04x}\n",
- i915_ggtt_offset(ce->ring->vma),
- ce->ring->head, ce->ring->tail);
-
- smp_mb__before_atomic(); /* flush pin before it is visible */
- atomic_inc(&ce->pin_count);
- }
-
- GEM_BUG_ON(!intel_context_is_pinned(ce)); /* no overflow! */
- GEM_BUG_ON(i915_active_is_idle(&ce->active));
- goto out_unlock;
-
-err_active:
- intel_context_active_release(ce);
-out_unlock:
- mutex_unlock(&ce->pin_mutex);
-out_release:
- i915_active_release(&ce->active);
- return err;
-}
-
-void intel_context_unpin(struct intel_context *ce)
-{
- if (!atomic_dec_and_test(&ce->pin_count))
- return;
-
- CE_TRACE(ce, "unpin\n");
- ce->ops->unpin(ce);
-
- /*
- * Once released, we may asynchronously drop the active reference.
- * As that may be the only reference keeping the context alive,
- * take an extra now so that it is not freed before we finish
- * dereferencing it.
- */
- intel_context_get(ce);
- intel_context_active_release(ce);
- intel_context_put(ce);
-}
-
static int __context_pin_state(struct i915_vma *vma)
{
unsigned int bias = i915_ggtt_pin_bias(vma) | PIN_OFFSET_BIAS;
@@ -225,6 +152,138 @@ static void __ring_retire(struct intel_ring *ring)
intel_ring_unpin(ring);
}
+static int intel_context_pre_pin(struct intel_context *ce)
+{
+ int err;
+
+ CE_TRACE(ce, "active\n");
+
+ err = __ring_active(ce->ring);
+ if (err)
+ return err;
+
+ err = intel_timeline_pin(ce->timeline);
+ if (err)
+ goto err_ring;
+
+ if (!ce->state)
+ return 0;
+
+ err = __context_pin_state(ce->state);
+ if (err)
+ goto err_timeline;
+
+
+ return 0;
+
+err_timeline:
+ intel_timeline_unpin(ce->timeline);
+err_ring:
+ __ring_retire(ce->ring);
+ return err;
+}
+
+static void intel_context_post_unpin(struct intel_context *ce)
+{
+ if (ce->state)
+ __context_unpin_state(ce->state);
+
+ intel_timeline_unpin(ce->timeline);
+ __ring_retire(ce->ring);
+}
+
+int __intel_context_do_pin(struct intel_context *ce)
+{
+ bool handoff = false;
+ void *vaddr;
+ int err = 0;
+
+ if (unlikely(!test_bit(CONTEXT_ALLOC_BIT, &ce->flags))) {
+ err = intel_context_alloc_state(ce);
+ if (err)
+ return err;
+ }
+
+ /*
+ * We always pin the context/ring/timeline here, to ensure a pin
+ * refcount for __intel_context_active(), which prevent a lock
+ * inversion of ce->pin_mutex vs dma_resv_lock().
+ */
+ err = intel_context_pre_pin(ce);
+ if (err)
+ return err;
+
+ err = i915_active_acquire(&ce->active);
+ if (err)
+ goto err_ctx_unpin;
+
+ err = ce->ops->pre_pin(ce, &vaddr);
+ if (err)
+ goto err_release;
+
+ err = mutex_lock_interruptible(&ce->pin_mutex);
+ if (err)
+ goto err_post_unpin;
+
+ if (unlikely(intel_context_is_closed(ce))) {
+ err = -ENOENT;
+ goto err_unlock;
+ }
+
+ if (likely(!atomic_add_unless(&ce->pin_count, 1, 0))) {
+ err = intel_context_active_acquire(ce);
+ if (unlikely(err))
+ goto err_unlock;
+
+ err = ce->ops->pin(ce, vaddr);
+ if (err) {
+ intel_context_active_release(ce);
+ goto err_unlock;
+ }
+
+ CE_TRACE(ce, "pin ring:{start:%08x, head:%04x, tail:%04x}\n",
+ i915_ggtt_offset(ce->ring->vma),
+ ce->ring->head, ce->ring->tail);
+
+ handoff = true;
+ smp_mb__before_atomic(); /* flush pin before it is visible */
+ atomic_inc(&ce->pin_count);
+ }
+
+ GEM_BUG_ON(!intel_context_is_pinned(ce)); /* no overflow! */
+
+err_unlock:
+ mutex_unlock(&ce->pin_mutex);
+err_post_unpin:
+ if (!handoff)
+ ce->ops->post_unpin(ce);
+err_release:
+ i915_active_release(&ce->active);
+err_ctx_unpin:
+ intel_context_post_unpin(ce);
+ return err;
+}
+
+void intel_context_unpin(struct intel_context *ce)
+{
+ if (!atomic_dec_and_test(&ce->pin_count))
+ return;
+
+ CE_TRACE(ce, "unpin\n");
+ ce->ops->unpin(ce);
+ ce->ops->post_unpin(ce);
What's protecting ops->unpin() here, running concurrently with ops->pin
in __intel_context_do_pin()? Do the ops functions have to implement
their own locking if needed?
Otherwise LGTM
Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxx>
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