Merge "Let producer gain posted buffer if no released buffer exist."

3 files changed, 293 insertions, 70 deletions

diff --git a/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp b/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp
index e1c1aa96c0..b8e2f9dec0 100644
--- a/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp
+++ b/libs/vr/libbufferhubqueue/buffer_hub_queue_client.cpp
@@ -69,7 +69,7 @@ void BufferHubQueue::Initialize() {
       .data = {.u64 = Stuff(-1, BufferHubQueue::kEpollQueueEventIndex)}};
   ret = epoll_fd_.Control(EPOLL_CTL_ADD, event_fd(), &event);
   if (ret < 0) {
-    ALOGE("BufferHubQueue::Initialize: Failed to add event fd to epoll set: %s",
+    ALOGE("%s: Failed to add event fd to epoll set: %s", __FUNCTION__,
           strerror(-ret));
   }
 }
@@ -77,7 +77,7 @@ void BufferHubQueue::Initialize() {
 Status<void> BufferHubQueue::ImportQueue() {
   auto status = InvokeRemoteMethod<BufferHubRPC::GetQueueInfo>();
   if (!status) {
-    ALOGE("BufferHubQueue::ImportQueue: Failed to import queue: %s",
+    ALOGE("%s: Failed to import queue: %s", __FUNCTION__,
           status.GetErrorMessage().c_str());
     return ErrorStatus(status.error());
   } else {
@@ -136,9 +136,7 @@ BufferHubQueue::CreateConsumerQueueParcelable(bool silent) {
       consumer_queue->GetChannel()->TakeChannelParcelable());
 
   if (!queue_parcelable.IsValid()) {
-    ALOGE(
-        "BufferHubQueue::CreateConsumerQueueParcelable: Failed to create "
-        "consumer queue parcelable.");
+    ALOGE("%s: Failed to create consumer queue parcelable.", __FUNCTION__);
     return ErrorStatus(EINVAL);
   }
 
@@ -169,8 +167,7 @@ bool BufferHubQueue::WaitForBuffers(int timeout) {
     }
 
     if (ret < 0 && ret != -EINTR) {
-      ALOGE("BufferHubQueue::WaitForBuffers: Failed to wait for buffers: %s",
-            strerror(-ret));
+      ALOGE("%s: Failed to wait for buffers: %s", __FUNCTION__, strerror(-ret));
       return false;
     }
 
@@ -264,14 +261,14 @@ Status<void> BufferHubQueue::HandleQueueEvent(int poll_event) {
     // wait will be tried again to acquire the newly imported buffer.
     auto buffer_status = OnBufferAllocated();
     if (!buffer_status) {
-      ALOGE("BufferHubQueue::HandleQueueEvent: Failed to import buffer: %s",
+      ALOGE("%s: Failed to import buffer: %s", __FUNCTION__,
             buffer_status.GetErrorMessage().c_str());
     }
   } else if (events & EPOLLHUP) {
-    ALOGD_IF(TRACE, "BufferHubQueue::HandleQueueEvent: hang up event!");
+    ALOGD_IF(TRACE, "%s: hang up event!", __FUNCTION__);
     hung_up_ = true;
   } else {
-    ALOGW("BufferHubQueue::HandleQueueEvent: Unknown epoll events=%x", events);
+    ALOGW("%s: Unknown epoll events=%x", __FUNCTION__, events);
   }
 
   return {};
@@ -279,12 +276,11 @@ Status<void> BufferHubQueue::HandleQueueEvent(int poll_event) {
 
 Status<void> BufferHubQueue::AddBuffer(
     const std::shared_ptr<BufferHubBase>& buffer, size_t slot) {
-  ALOGD_IF(TRACE, "BufferHubQueue::AddBuffer: buffer_id=%d slot=%zu",
-           buffer->id(), slot);
+  ALOGD_IF(TRACE, "%s: buffer_id=%d slot=%zu", __FUNCTION__, buffer->id(),
+           slot);
 
   if (is_full()) {
-    ALOGE("BufferHubQueue::AddBuffer queue is at maximum capacity: %zu",
-          capacity_);
+    ALOGE("%s: queue is at maximum capacity: %zu", __FUNCTION__, capacity_);
     return ErrorStatus(E2BIG);
   }
 
@@ -303,7 +299,7 @@ Status<void> BufferHubQueue::AddBuffer(
     const int ret =
         epoll_fd_.Control(EPOLL_CTL_ADD, event_source.event_fd, &event);
     if (ret < 0) {
-      ALOGE("BufferHubQueue::AddBuffer: Failed to add buffer to epoll set: %s",
+      ALOGE("%s: Failed to add buffer to epoll set: %s", __FUNCTION__,
             strerror(-ret));
       return ErrorStatus(-ret);
     }
@@ -315,17 +311,15 @@ Status<void> BufferHubQueue::AddBuffer(
 }
 
 Status<void> BufferHubQueue::RemoveBuffer(size_t slot) {
-  ALOGD_IF(TRACE, "BufferHubQueue::RemoveBuffer: slot=%zu", slot);
+  ALOGD_IF(TRACE, "%s: slot=%zu", __FUNCTION__, slot);
 
   if (buffers_[slot]) {
     for (const auto& event_source : buffers_[slot]->GetEventSources()) {
       const int ret =
           epoll_fd_.Control(EPOLL_CTL_DEL, event_source.event_fd, nullptr);
       if (ret < 0) {
-        ALOGE(
-            "BufferHubQueue::RemoveBuffer: Failed to remove buffer from epoll "
-            "set: %s",
-            strerror(-ret));
+        ALOGE("%s: Failed to remove buffer from epoll set: %s", __FUNCTION__,
+              strerror(-ret));
         return ErrorStatus(-ret);
       }
     }
@@ -345,23 +339,31 @@ Status<void> BufferHubQueue::Enqueue(Entry entry) {
   if (!is_full()) {
     available_buffers_.push(std::move(entry));
 
+    // Find and remove the enqueued buffer from unavailable_buffers_slot if
+    // exist.
+    auto enqueued_buffer_iter = std::find_if(
+        unavailable_buffers_slot_.begin(), unavailable_buffers_slot_.end(),
+        [&entry](size_t slot) -> bool { return slot == entry.slot; });
+    if (enqueued_buffer_iter != unavailable_buffers_slot_.end()) {
+      unavailable_buffers_slot_.erase(enqueued_buffer_iter);
+    }
+
     // Trigger OnBufferAvailable callback if registered.
     if (on_buffer_available_)
       on_buffer_available_();
 
     return {};
   } else {
-    ALOGE("BufferHubQueue::Enqueue: Buffer queue is full!");
+    ALOGE("%s: Buffer queue is full!", __FUNCTION__);
     return ErrorStatus(E2BIG);
   }
 }
 
 Status<std::shared_ptr<BufferHubBase>> BufferHubQueue::Dequeue(int timeout,
                                                                size_t* slot) {
-  ALOGD_IF(TRACE, "BufferHubQueue::Dequeue: count=%zu, timeout=%d", count(),
-           timeout);
+  ALOGD_IF(TRACE, "%s: count=%zu, timeout=%d", __FUNCTION__, count(), timeout);
 
-  PDX_TRACE_FORMAT("BufferHubQueue::Dequeue|count=%zu|", count());
+  PDX_TRACE_FORMAT("%s|count=%zu|", __FUNCTION__, count());
 
   if (count() == 0) {
     if (!WaitForBuffers(timeout))
@@ -376,6 +378,7 @@ Status<std::shared_ptr<BufferHubBase>> BufferHubQueue::Dequeue(int timeout,
   *slot = entry.slot;
 
   available_buffers_.pop();
+  unavailable_buffers_slot_.push_back(*slot);
 
   return {std::move(buffer)};
 }
@@ -564,7 +567,7 @@ Status<void> ProducerQueue::RemoveBuffer(size_t slot) {
   auto status =
       InvokeRemoteMethod<BufferHubRPC::ProducerQueueRemoveBuffer>(slot);
   if (!status) {
-    ALOGE("ProducerQueue::RemoveBuffer: Failed to remove producer buffer: %s",
+    ALOGE("%s: Failed to remove producer buffer: %s", __FUNCTION__,
           status.GetErrorMessage().c_str());
     return status.error_status();
   }
@@ -580,31 +583,81 @@ Status<std::shared_ptr<BufferProducer>> ProducerQueue::Dequeue(
 
 pdx::Status<std::shared_ptr<BufferProducer>> ProducerQueue::Dequeue(
     int timeout, size_t* slot, DvrNativeBufferMetadata* out_meta,
-    pdx::LocalHandle* release_fence) {
+    pdx::LocalHandle* release_fence, bool gain_posted_buffer) {
   ATRACE_NAME("ProducerQueue::Dequeue");
   if (slot == nullptr || out_meta == nullptr || release_fence == nullptr) {
-    ALOGE("ProducerQueue::Dequeue: Invalid parameter.");
+    ALOGE("%s: Invalid parameter.", __FUNCTION__);
     return ErrorStatus(EINVAL);
   }
 
-  auto status = BufferHubQueue::Dequeue(timeout, slot);
-  if (!status)
-    return status.error_status();
-
-  auto buffer = std::static_pointer_cast<BufferProducer>(status.take());
-  const int ret = buffer->GainAsync(out_meta, release_fence);
+  std::shared_ptr<BufferProducer> buffer;
+  Status<std::shared_ptr<BufferHubBase>> dequeue_status =
+      BufferHubQueue::Dequeue(timeout, slot);
+  if (dequeue_status.ok()) {
+    buffer = std::static_pointer_cast<BufferProducer>(dequeue_status.take());
+  } else {
+    if (gain_posted_buffer) {
+      Status<std::shared_ptr<BufferProducer>> dequeue_unacquired_status =
+          ProducerQueue::DequeueUnacquiredBuffer(slot);
+      if (!dequeue_unacquired_status.ok()) {
+        ALOGE("%s: DequeueUnacquiredBuffer returned error: %d", __FUNCTION__,
+              dequeue_unacquired_status.error());
+        return dequeue_unacquired_status.error_status();
+      }
+      buffer = dequeue_unacquired_status.take();
+    } else {
+      return dequeue_status.error_status();
+    }
+  }
+  const int ret =
+      buffer->GainAsync(out_meta, release_fence, gain_posted_buffer);
   if (ret < 0 && ret != -EALREADY)
     return ErrorStatus(-ret);
 
   return {std::move(buffer)};
 }
 
+Status<std::shared_ptr<BufferProducer>> ProducerQueue::DequeueUnacquiredBuffer(
+    size_t* slot) {
+  if (unavailable_buffers_slot_.size() < 1) {
+    ALOGE(
+        "%s: Failed to dequeue un-acquired buffer. All buffer(s) are in "
+        "acquired state if exist.",
+        __FUNCTION__);
+    return ErrorStatus(ENOMEM);
+  }
+
+  // Find the first buffer that is not in acquired state from
+  // unavailable_buffers_slot_.
+  for (auto iter = unavailable_buffers_slot_.begin();
+       iter != unavailable_buffers_slot_.end(); iter++) {
+    std::shared_ptr<BufferProducer> buffer = ProducerQueue::GetBuffer(*iter);
+    if (buffer == nullptr) {
+      ALOGE("%s failed. Buffer slot %d is  null.", __FUNCTION__,
+            static_cast<int>(*slot));
+      return ErrorStatus(EIO);
+    }
+    if (!BufferHubDefs::IsBufferAcquired(buffer->buffer_state())) {
+      *slot = *iter;
+      unavailable_buffers_slot_.erase(iter);
+      unavailable_buffers_slot_.push_back(*slot);
+      ALOGD("%s: Producer queue dequeue unacquired buffer in slot %d",
+            __FUNCTION__, static_cast<int>(*slot));
+      return {std::move(buffer)};
+    }
+  }
+  ALOGE(
+      "%s: Failed to dequeue un-acquired buffer. No un-acquired buffer exist.",
+      __FUNCTION__);
+  return ErrorStatus(EBUSY);
+}
+
 pdx::Status<ProducerQueueParcelable> ProducerQueue::TakeAsParcelable() {
   if (capacity() != 0) {
     ALOGE(
-        "ProducerQueue::TakeAsParcelable: producer queue can only be taken out"
-        " as a parcelable when empty. Current queue capacity: %zu",
-        capacity());
+        "%s: producer queue can only be taken out as a parcelable when empty. "
+        "Current queue capacity: %zu",
+        __FUNCTION__, capacity());
     return ErrorStatus(EINVAL);
   }
 
@@ -628,17 +681,16 @@ ConsumerQueue::ConsumerQueue(LocalChannelHandle handle)
     : BufferHubQueue(std::move(handle)) {
   auto status = ImportQueue();
   if (!status) {
-    ALOGE("ConsumerQueue::ConsumerQueue: Failed to import queue: %s",
+    ALOGE("%s: Failed to import queue: %s", __FUNCTION__,
           status.GetErrorMessage().c_str());
     Close(-status.error());
   }
 
   auto import_status = ImportBuffers();
   if (import_status) {
-    ALOGI("ConsumerQueue::ConsumerQueue: Imported %zu buffers.",
-          import_status.get());
+    ALOGI("%s: Imported %zu buffers.", __FUNCTION__, import_status.get());
   } else {
-    ALOGE("ConsumerQueue::ConsumerQueue: Failed to import buffers: %s",
+    ALOGE("%s: Failed to import buffers: %s", __FUNCTION__,
           import_status.GetErrorMessage().c_str());
   }
 }
@@ -647,14 +699,11 @@ Status<size_t> ConsumerQueue::ImportBuffers() {
   auto status = InvokeRemoteMethod<BufferHubRPC::ConsumerQueueImportBuffers>();
   if (!status) {
     if (status.error() == EBADR) {
-      ALOGI(
-          "ConsumerQueue::ImportBuffers: Queue is silent, no buffers "
-          "imported.");
+      ALOGI("%s: Queue is silent, no buffers imported.", __FUNCTION__);
       return {0};
     } else {
-      ALOGE(
-          "ConsumerQueue::ImportBuffers: Failed to import consumer buffer: %s",
-          status.GetErrorMessage().c_str());
+      ALOGE("%s: Failed to import consumer buffer: %s", __FUNCTION__,
+            status.GetErrorMessage().c_str());
       return status.error_status();
     }
   }
@@ -665,13 +714,13 @@ Status<size_t> ConsumerQueue::ImportBuffers() {
 
   auto buffer_handle_slots = status.take();
   for (auto& buffer_handle_slot : buffer_handle_slots) {
-    ALOGD_IF(TRACE, "ConsumerQueue::ImportBuffers: buffer_handle=%d",
+    ALOGD_IF(TRACE, ": buffer_handle=%d", __FUNCTION__,
              buffer_handle_slot.first.value());
 
     std::unique_ptr<BufferConsumer> buffer_consumer =
         BufferConsumer::Import(std::move(buffer_handle_slot.first));
     if (!buffer_consumer) {
-      ALOGE("ConsumerQueue::ImportBuffers: Failed to import buffer: slot=%zu",
+      ALOGE("%s: Failed to import buffer: slot=%zu", __FUNCTION__,
             buffer_handle_slot.second);
       last_error = ErrorStatus(EPIPE);
       continue;
@@ -680,7 +729,7 @@ Status<size_t> ConsumerQueue::ImportBuffers() {
     auto add_status =
         AddBuffer(std::move(buffer_consumer), buffer_handle_slot.second);
     if (!add_status) {
-      ALOGE("ConsumerQueue::ImportBuffers: Failed to add buffer: %s",
+      ALOGE("%s: Failed to add buffer: %s", __FUNCTION__,
             add_status.GetErrorMessage().c_str());
       last_error = add_status;
     } else {
@@ -696,8 +745,8 @@ Status<size_t> ConsumerQueue::ImportBuffers() {
 
 Status<void> ConsumerQueue::AddBuffer(
     const std::shared_ptr<BufferConsumer>& buffer, size_t slot) {
-  ALOGD_IF(TRACE, "ConsumerQueue::AddBuffer: queue_id=%d buffer_id=%d slot=%zu",
-           id(), buffer->id(), slot);
+  ALOGD_IF(TRACE, "%s: queue_id=%d buffer_id=%d slot=%zu", __FUNCTION__, id(),
+           buffer->id(), slot);
   return BufferHubQueue::AddBuffer(buffer, slot);
 }
 
@@ -706,9 +755,9 @@ Status<std::shared_ptr<BufferConsumer>> ConsumerQueue::Dequeue(
     LocalHandle* acquire_fence) {
   if (user_metadata_size != user_metadata_size_) {
     ALOGE(
-        "ConsumerQueue::Dequeue: Metadata size (%zu) for the dequeuing buffer "
-        "does not match metadata size (%zu) for the queue.",
-        user_metadata_size, user_metadata_size_);
+        "%s: Metadata size (%zu) for the dequeuing buffer does not match "
+        "metadata size (%zu) for the queue.",
+        __FUNCTION__, user_metadata_size, user_metadata_size_);
     return ErrorStatus(EINVAL);
   }
 
@@ -723,7 +772,7 @@ Status<std::shared_ptr<BufferConsumer>> ConsumerQueue::Dequeue(
     if (metadata_src) {
       memcpy(meta, metadata_src, user_metadata_size);
     } else {
-      ALOGW("ConsumerQueue::Dequeue: no user-defined metadata.");
+      ALOGW("%s: no user-defined metadata.", __FUNCTION__);
     }
   }
 
@@ -735,7 +784,7 @@ Status<std::shared_ptr<BufferConsumer>> ConsumerQueue::Dequeue(
     pdx::LocalHandle* acquire_fence) {
   ATRACE_NAME("ConsumerQueue::Dequeue");
   if (slot == nullptr || out_meta == nullptr || acquire_fence == nullptr) {
-    ALOGE("ConsumerQueue::Dequeue: Invalid parameter.");
+    ALOGE("%s: Invalid parameter.", __FUNCTION__);
     return ErrorStatus(EINVAL);
   }
 
@@ -752,19 +801,18 @@ Status<std::shared_ptr<BufferConsumer>> ConsumerQueue::Dequeue(
 }
 
 Status<void> ConsumerQueue::OnBufferAllocated() {
-  ALOGD_IF(TRACE, "ConsumerQueue::OnBufferAllocated: queue_id=%d", id());
+  ALOGD_IF(TRACE, "%s: queue_id=%d", __FUNCTION__, id());
 
   auto status = ImportBuffers();
   if (!status) {
-    ALOGE("ConsumerQueue::OnBufferAllocated: Failed to import buffers: %s",
+    ALOGE("%s: Failed to import buffers: %s", __FUNCTION__,
           status.GetErrorMessage().c_str());
     return ErrorStatus(status.error());
   } else if (status.get() == 0) {
-    ALOGW("ConsumerQueue::OnBufferAllocated: No new buffers allocated!");
+    ALOGW("%s: No new buffers allocated!", __FUNCTION__);
     return ErrorStatus(ENOBUFS);
   } else {
-    ALOGD_IF(TRACE,
-             "ConsumerQueue::OnBufferAllocated: Imported %zu consumer buffers.",
+    ALOGD_IF(TRACE, "%s: Imported %zu consumer buffers.", __FUNCTION__,
              status.get());
     return {};
   }
diff --git a/libs/vr/libbufferhubqueue/include/private/dvr/buffer_hub_queue_client.h b/libs/vr/libbufferhubqueue/include/private/dvr/buffer_hub_queue_client.h
index c69002debd..def7c6b66e 100644
--- a/libs/vr/libbufferhubqueue/include/private/dvr/buffer_hub_queue_client.h
+++ b/libs/vr/libbufferhubqueue/include/private/dvr/buffer_hub_queue_client.h
@@ -57,10 +57,10 @@ class BufferHubQueue : public pdx::Client {
   uint32_t default_width() const { return default_width_; }
 
   // Returns the default buffer height of this buffer queue.
-  uint32_t default_height() const { return static_cast<uint32_t>(default_height_); }
+  uint32_t default_height() const { return default_height_; }
 
   // Returns the default buffer format of this buffer queue.
-  uint32_t default_format() const { return static_cast<uint32_t>(default_format_); }
+  uint32_t default_format() const { return default_format_; }
 
   // Creates a new consumer in handle form for immediate transport over RPC.
   pdx::Status<pdx::LocalChannelHandle> CreateConsumerQueueHandle(
@@ -208,6 +208,14 @@ class BufferHubQueue : public pdx::Client {
   // Size of the metadata that buffers in this queue cary.
   size_t user_metadata_size_{0};
 
+  // Buffers and related data that are available for dequeue.
+  std::priority_queue<Entry, std::vector<Entry>, EntryComparator>
+      available_buffers_;
+
+  // Slot of the buffers that are not available for normal dequeue. For example,
+  // the slot of posted or acquired buffers in the perspective of a producer.
+  std::vector<size_t> unavailable_buffers_slot_;
+
  private:
   void Initialize();
 
@@ -252,10 +260,6 @@ class BufferHubQueue : public pdx::Client {
   // queue regardless of its queue position or presence in the ring buffer.
   std::array<std::shared_ptr<BufferHubBase>, kMaxQueueCapacity> buffers_;
 
-  // Buffers and related data that are available for dequeue.
-  std::priority_queue<Entry, std::vector<Entry>, EntryComparator>
-      available_buffers_;
-
   // Keeps track with how many buffers have been added into the queue.
   size_t capacity_{0};
 
@@ -349,11 +353,30 @@ class ProducerQueue : public pdx::ClientBase<ProducerQueue, BufferHubQueue> {
   // Dequeue a producer buffer to write. The returned buffer in |Gain|'ed mode,
   // and caller should call Post() once it's done writing to release the buffer
   // to the consumer side.
+  // @return a buffer in gained state, which was originally in released state.
   pdx::Status<std::shared_ptr<BufferProducer>> Dequeue(
       int timeout, size_t* slot, pdx::LocalHandle* release_fence);
+
+  // Dequeue a producer buffer to write. The returned buffer in |Gain|'ed mode,
+  // and caller should call Post() once it's done writing to release the buffer
+  // to the consumer side.
+  //
+  // @param timeout to dequeue a buffer.
+  // @param slot is the slot of the output BufferProducer.
+  // @param release_fence for gaining a buffer.
+  // @param out_meta metadata of the output buffer.
+  // @param gain_posted_buffer whether to gain posted buffer if no released
+  //     buffer is available to gain.
+  // @return a buffer in gained state, which was originally in released state if
+  //     gain_posted_buffer is false, or in posted/released state if
+  //     gain_posted_buffer is true.
+  // TODO(b/112007999): gain_posted_buffer true is only used to prevent
+  // libdvrtracking from starving when there are non-responding clients. This
+  // gain_posted_buffer param can be removed once libdvrtracking start to use
+  // the new AHardwareBuffer API.
   pdx::Status<std::shared_ptr<BufferProducer>> Dequeue(
       int timeout, size_t* slot, DvrNativeBufferMetadata* out_meta,
-      pdx::LocalHandle* release_fence);
+      pdx::LocalHandle* release_fence, bool gain_posted_buffer = false);
 
   // Enqueues a producer buffer in the queue.
   pdx::Status<void> Enqueue(const std::shared_ptr<BufferProducer>& buffer,
@@ -374,6 +397,16 @@ class ProducerQueue : public pdx::ClientBase<ProducerQueue, BufferHubQueue> {
   // arguments as the constructors.
   explicit ProducerQueue(pdx::LocalChannelHandle handle);
   ProducerQueue(const ProducerQueueConfig& config, const UsagePolicy& usage);
+
+  // Dequeue a producer buffer to write. The returned buffer in |Gain|'ed mode,
+  // and caller should call Post() once it's done writing to release the buffer
+  // to the consumer side.
+  //
+  // @param slot the slot of the returned buffer.
+  // @return a buffer in gained state, which was originally in posted state or
+  //     released state.
+  pdx::Status<std::shared_ptr<BufferProducer>> DequeueUnacquiredBuffer(
+      size_t* slot);
 };
 
 class ConsumerQueue : public BufferHubQueue {
diff --git a/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp b/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp
index 046df5412f..c58f55f7bd 100644
--- a/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp
+++ b/libs/vr/libbufferhubqueue/tests/buffer_hub_queue-test.cpp
@@ -1,5 +1,6 @@
 #include <base/logging.h>
 #include <binder/Parcel.h>
+#include <dvr/dvr_api.h>
 #include <private/dvr/buffer_hub_client.h>
 #include <private/dvr/buffer_hub_queue_client.h>
 
@@ -122,6 +123,147 @@ TEST_F(BufferHubQueueTest, TestDequeue) {
   }
 }
 
+TEST_F(BufferHubQueueTest,
+       TestDequeuePostedBufferIfNoAvailableReleasedBuffer_withBufferConsumer) {
+  ASSERT_TRUE(CreateQueues(config_builder_.Build(), UsagePolicy{}));
+
+  // Allocate 3 buffers to use.
+  const size_t test_queue_capacity = 3;
+  for (int64_t i = 0; i < test_queue_capacity; i++) {
+    AllocateBuffer();
+  }
+  EXPECT_EQ(producer_queue_->capacity(), test_queue_capacity);
+
+  size_t producer_slot, consumer_slot;
+  LocalHandle fence;
+  DvrNativeBufferMetadata mi, mo;
+
+  // Producer posts 2 buffers and remember their posted sequence.
+  std::deque<size_t> posted_slots;
+  for (int64_t i = 0; i < 2; i++) {
+    auto p1_status =
+        producer_queue_->Dequeue(kTimeoutMs, &producer_slot, &mo, &fence, true);
+    EXPECT_TRUE(p1_status.ok());
+    auto p1 = p1_status.take();
+    ASSERT_NE(p1, nullptr);
+
+    // Producer should not be gaining posted buffer when there are still
+    // available buffers to gain.
+    auto found_iter =
+        std::find(posted_slots.begin(), posted_slots.end(), producer_slot);
+    EXPECT_EQ(found_iter, posted_slots.end());
+    posted_slots.push_back(producer_slot);
+
+    // Producer posts the buffer.
+    mi.index = i;
+    EXPECT_EQ(0, p1->PostAsync(&mi, LocalHandle()));
+  }
+
+  // Consumer acquires one buffer.
+  auto c1_status =
+      consumer_queue_->Dequeue(kTimeoutMs, &consumer_slot, &mo, &fence);
+  EXPECT_TRUE(c1_status.ok());
+  auto c1 = c1_status.take();
+  ASSERT_NE(c1, nullptr);
+  // Consumer should get the oldest posted buffer. No checks here.
+  // posted_slots[0] should be in acquired state now.
+  EXPECT_EQ(mo.index, 0);
+  // Consumer releases the buffer.
+  EXPECT_EQ(c1->ReleaseAsync(&mi, LocalHandle()), 0);
+  // posted_slots[0] should be in released state now.
+
+  // Producer gain and post 2 buffers.
+  for (int64_t i = 0; i < 2; i++) {
+    auto p1_status =
+        producer_queue_->Dequeue(kTimeoutMs, &producer_slot, &mo, &fence, true);
+    EXPECT_TRUE(p1_status.ok());
+    auto p1 = p1_status.take();
+    ASSERT_NE(p1, nullptr);
+
+    // The gained buffer should be the one in released state or the one haven't
+    // been use.
+    EXPECT_NE(posted_slots[1], producer_slot);
+
+    mi.index = i + 2;
+    EXPECT_EQ(0, p1->PostAsync(&mi, LocalHandle()));
+  }
+
+  // Producer gains a buffer.
+  auto p1_status =
+      producer_queue_->Dequeue(kTimeoutMs, &producer_slot, &mo, &fence, true);
+  EXPECT_TRUE(p1_status.ok());
+  auto p1 = p1_status.take();
+  ASSERT_NE(p1, nullptr);
+
+  // The gained buffer should be the oldest posted buffer.
+  EXPECT_EQ(posted_slots[1], producer_slot);
+
+  // Producer posts the buffer.
+  mi.index = 4;
+  EXPECT_EQ(0, p1->PostAsync(&mi, LocalHandle()));
+}
+
+TEST_F(BufferHubQueueTest,
+       TestDequeuePostedBufferIfNoAvailableReleasedBuffer_noBufferConsumer) {
+  ASSERT_TRUE(CreateQueues(config_builder_.Build(), UsagePolicy{}));
+
+  // Allocate 4 buffers to use.
+  const size_t test_queue_capacity = 4;
+  for (int64_t i = 0; i < test_queue_capacity; i++) {
+    AllocateBuffer();
+  }
+  EXPECT_EQ(producer_queue_->capacity(), test_queue_capacity);
+
+  // Post all allowed buffers and remember their posted sequence.
+  std::deque<size_t> posted_slots;
+  for (int64_t i = 0; i < test_queue_capacity; i++) {
+    size_t slot;
+    LocalHandle fence;
+    DvrNativeBufferMetadata mi, mo;
+
+    // Producer gains a buffer.
+    auto p1_status =
+        producer_queue_->Dequeue(kTimeoutMs, &slot, &mo, &fence, true);
+    EXPECT_TRUE(p1_status.ok());
+    auto p1 = p1_status.take();
+    ASSERT_NE(p1, nullptr);
+
+    // Producer should not be gaining posted buffer when there are still
+    // available buffers to gain.
+    auto found_iter = std::find(posted_slots.begin(), posted_slots.end(), slot);
+    EXPECT_EQ(found_iter, posted_slots.end());
+    posted_slots.push_back(slot);
+
+    // Producer posts the buffer.
+    mi.index = i;
+    EXPECT_EQ(p1->PostAsync(&mi, LocalHandle()), 0);
+  }
+
+  // Gain posted buffers in sequence.
+  const int64_t nb_dequeue_all_times = 2;
+  for (int j = 0; j < nb_dequeue_all_times; ++j) {
+    for (int i = 0; i < test_queue_capacity; ++i) {
+      size_t slot;
+      LocalHandle fence;
+      DvrNativeBufferMetadata mi, mo;
+
+      // Producer gains a buffer.
+      auto p1_status =
+          producer_queue_->Dequeue(kTimeoutMs, &slot, &mo, &fence, true);
+      EXPECT_TRUE(p1_status.ok());
+      auto p1 = p1_status.take();
+      ASSERT_NE(p1, nullptr);
+
+      // The gained buffer should be the oldest posted buffer.
+      EXPECT_EQ(posted_slots[i], slot);
+
+      // Producer posts the buffer.
+      mi.index = i + test_queue_capacity * (j + 1);
+      EXPECT_EQ(p1->PostAsync(&mi, LocalHandle()), 0);
+    }
+  }
+}
+
 TEST_F(BufferHubQueueTest, TestProducerConsumer) {
   const size_t kBufferCount = 16;
   size_t slot;
@@ -245,8 +387,8 @@ TEST_F(BufferHubQueueTest, TestRemoveBuffer) {
 
   for (size_t i = 0; i < kBufferCount; i++) {
     Entry* entry = &buffers[i];
-    auto producer_status = producer_queue_->Dequeue(
-        kTimeoutMs, &entry->slot, &mo, &entry->fence);
+    auto producer_status =
+        producer_queue_->Dequeue(kTimeoutMs, &entry->slot, &mo, &entry->fence);
     ASSERT_TRUE(producer_status.ok());
     entry->buffer = producer_status.take();
     ASSERT_NE(nullptr, entry->buffer);