DO NOT MERGE: Move blast sync handling to BBQ

Add logic in BBQ so it can handle waiting the transaction callback vs a
sync transaction request. The following behavior will occur

1. If a nextTransaction (sync) was set, we will wait until the
transaction callback for that frame before continuing to acquire
new frames. Once the transaction callback for the sync transaction is
invoked, BBQ will flush the shadow queue. It will try to process
as many frames as it can that were queued up during the time BBQ was
blocked from processing.

2. If BBQ is waiting on a sync transaction callback and then another
sync transaction is requested afterwards, BBQ will allow it to acquire
a buffer instead of just adding to the shadow queue. It will acquire
the new frame in the new sync transaction and allow the caller that
requested the sync to apply it. At this point, it's up to the callers
to ensure they apply the two sync transactions in order to ensure
frames are applied in order.

3. Similar to 2, but if there are queue requests in between the two
sync requests that aren't trying to be synced. When the second sync
frame is getting acquired, BBQ will acquire and release any frames
that were requested in between. This is so we don't skip or
have to wait in the first sync transaction callback.

Test: BLASTBufferQueueTest
Bug: 200285149
Change-Id: I8da8de1a3fe2a44ca2199ff92cfd4b60c7f01183
(cherry picked from commit d7deef7278f934a1750738b600c11c1771ae7ac6)

1 files changed, 135 insertions, 25 deletions

diff --git a/libs/gui/BLASTBufferQueue.cpp b/libs/gui/BLASTBufferQueue.cpp
index e8e664bd76..94864e53f3 100644
--- a/libs/gui/BLASTBufferQueue.cpp
+++ b/libs/gui/BLASTBufferQueue.cpp
@@ -46,6 +46,8 @@ inline const char* boolToString(bool b) {
 namespace android {
 
 // Macros to include adapter info in log messages
+#define BQA_LOGD(x, ...) \
+    ALOGD("[%s](f:%u,a:%u) " x, mName.c_str(), mNumFrameAvailable, mNumAcquired, ##__VA_ARGS__)
 #define BQA_LOGV(x, ...) \
     ALOGV("[%s](f:%u,a:%u) " x, mName.c_str(), mNumFrameAvailable, mNumAcquired, ##__VA_ARGS__)
 // enable logs for a single layer
@@ -243,6 +245,67 @@ void BLASTBufferQueue::update(const sp<SurfaceControl>& surface, uint32_t width,
     }
 }
 
+static std::optional<SurfaceControlStats> findMatchingStat(
+        const std::vector<SurfaceControlStats>& stats, const sp<SurfaceControl>& sc) {
+    for (auto stat : stats) {
+        if (SurfaceControl::isSameSurface(sc, stat.surfaceControl)) {
+            return stat;
+        }
+    }
+    return std::nullopt;
+}
+
+static void transactionCommittedCallbackThunk(void* context, nsecs_t latchTime,
+                                              const sp<Fence>& presentFence,
+                                              const std::vector<SurfaceControlStats>& stats) {
+    if (context == nullptr) {
+        return;
+    }
+    sp<BLASTBufferQueue> bq = static_cast<BLASTBufferQueue*>(context);
+    bq->transactionCommittedCallback(latchTime, presentFence, stats);
+}
+
+void BLASTBufferQueue::transactionCommittedCallback(nsecs_t /*latchTime*/,
+                                                    const sp<Fence>& /*presentFence*/,
+                                                    const std::vector<SurfaceControlStats>& stats) {
+    {
+        std::unique_lock _lock{mMutex};
+        ATRACE_CALL();
+        BQA_LOGV("transactionCommittedCallback");
+        if (!mSurfaceControlsWithPendingCallback.empty()) {
+            sp<SurfaceControl> pendingSC = mSurfaceControlsWithPendingCallback.front();
+            std::optional<SurfaceControlStats> stat = findMatchingStat(stats, pendingSC);
+            if (stat) {
+                uint64_t currFrameNumber = stat->frameEventStats.frameNumber;
+
+                // We need to check if we were waiting for a transaction callback in order to
+                // process any pending buffers and unblock. It's possible to get transaction
+                // callbacks for previous requests so we need to ensure the frame from this
+                // transaction callback matches the last acquired buffer. Since acquireNextBuffer
+                // will stop processing buffers when mWaitForTransactionCallback is set, we know
+                // that mLastAcquiredFrameNumber is the frame we're waiting on.
+                // We also want to check if mNextTransaction is null because it's possible another
+                // sync request came in while waiting, but it hasn't started processing yet. In that
+                // case, we don't actually want to flush the frames in between since they will get
+                // processed and merged with the sync transaction and released earlier than if they
+                // were sent to SF
+                if (mWaitForTransactionCallback && mNextTransaction == nullptr &&
+                    currFrameNumber >= mLastAcquiredFrameNumber) {
+                    mWaitForTransactionCallback = false;
+                    flushShadowQueueLocked();
+                }
+            } else {
+                BQA_LOGE("Failed to find matching SurfaceControl in transaction callback");
+            }
+        } else {
+            BQA_LOGE("No matching SurfaceControls found: mSurfaceControlsWithPendingCallback was "
+                     "empty.");
+        }
+
+        decStrong((void*)transactionCommittedCallbackThunk);
+    }
+}
+
 static void transactionCallbackThunk(void* context, nsecs_t latchTime,
                                      const sp<Fence>& presentFence,
                                      const std::vector<SurfaceControlStats>& stats) {
@@ -266,12 +329,9 @@ void BLASTBufferQueue::transactionCallback(nsecs_t /*latchTime*/, const sp<Fence
         if (!mSurfaceControlsWithPendingCallback.empty()) {
             sp<SurfaceControl> pendingSC = mSurfaceControlsWithPendingCallback.front();
             mSurfaceControlsWithPendingCallback.pop();
-            bool found = false;
-            for (auto stat : stats) {
-                if (!SurfaceControl::isSameSurface(pendingSC, stat.surfaceControl)) {
-                    continue;
-                }
-
+            std::optional<SurfaceControlStats> statsOptional = findMatchingStat(stats, pendingSC);
+            if (statsOptional) {
+                SurfaceControlStats stat = *statsOptional;
                 mTransformHint = stat.transformHint;
                 mBufferItemConsumer->setTransformHint(mTransformHint);
                 BQA_LOGV("updated mTransformHint=%d", mTransformHint);
@@ -299,12 +359,7 @@ void BLASTBufferQueue::transactionCallback(nsecs_t /*latchTime*/, const sp<Fence
                     transactionCompleteCallback = std::move(mTransactionCompleteCallback);
                     mTransactionCompleteFrameNumber = 0;
                 }
-
-                found = true;
-                break;
-            }
-
-            if (!found) {
+            } else {
                 BQA_LOGE("Failed to find matching SurfaceControl in transaction callback");
             }
         } else {
@@ -336,6 +391,20 @@ static void releaseBufferCallbackThunk(wp<BLASTBufferQueue> context, const Relea
     }
 }
 
+void BLASTBufferQueue::flushShadowQueueLocked() {
+    BQA_LOGV("flushShadowQueueLocked");
+    int numFramesToFlush = mNumFrameAvailable;
+    while (numFramesToFlush > 0) {
+        acquireNextBufferLocked(std::nullopt);
+        numFramesToFlush--;
+    }
+}
+
+void BLASTBufferQueue::flushShadowQueue() {
+    std::unique_lock _lock{mMutex};
+    flushShadowQueueLocked();
+}
+
 void BLASTBufferQueue::releaseBufferCallback(const ReleaseCallbackId& id,
                                              const sp<Fence>& releaseFence, uint32_t transformHint,
                                              uint32_t currentMaxAcquiredBufferCount) {
@@ -377,7 +446,11 @@ void BLASTBufferQueue::releaseBufferCallback(const ReleaseCallbackId& id,
         BQA_LOGV("released %s", id.to_string().c_str());
         mBufferItemConsumer->releaseBuffer(it->second, releaseBuffer.releaseFence);
         mSubmitted.erase(it);
-        processNextBufferLocked(false /* useNextTransaction */);
+        // Don't process the transactions here if mWaitForTransactionCallback is set. Instead, let
+        // onFrameAvailable handle processing them since it will merge with the nextTransaction.
+        if (!mWaitForTransactionCallback) {
+            acquireNextBufferLocked(std::nullopt);
+        }
     }
 
     ATRACE_INT("PendingRelease", mPendingRelease.size());
@@ -386,13 +459,15 @@ void BLASTBufferQueue::releaseBufferCallback(const ReleaseCallbackId& id,
     mCallbackCV.notify_all();
 }
 
-void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
+void BLASTBufferQueue::acquireNextBufferLocked(
+        const std::optional<SurfaceComposerClient::Transaction*> transaction) {
     ATRACE_CALL();
     // If the next transaction is set, we want to guarantee the our acquire will not fail, so don't
     // include the extra buffer when checking if we can acquire the next buffer.
-    const bool includeExtraAcquire = !useNextTransaction;
-    if (mNumFrameAvailable == 0 || maxBuffersAcquired(includeExtraAcquire)) {
-        mCallbackCV.notify_all();
+    const bool includeExtraAcquire = !transaction;
+    const bool maxAcquired = maxBuffersAcquired(includeExtraAcquire);
+    if (mNumFrameAvailable == 0 || maxAcquired) {
+        BQA_LOGV("Can't process next buffer maxBuffersAcquired=%s", boolToString(maxAcquired));
         return;
     }
 
@@ -404,9 +479,8 @@ void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
     SurfaceComposerClient::Transaction localTransaction;
     bool applyTransaction = true;
     SurfaceComposerClient::Transaction* t = &localTransaction;
-    if (mNextTransaction != nullptr && useNextTransaction) {
-        t = mNextTransaction;
-        mNextTransaction = nullptr;
+    if (transaction) {
+        t = *transaction;
         applyTransaction = false;
     }
 
@@ -436,7 +510,7 @@ void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
                  mSize.width, mSize.height, mRequestedSize.width, mRequestedSize.height,
                  buffer->getWidth(), buffer->getHeight(), bufferItem.mTransform);
         mBufferItemConsumer->releaseBuffer(bufferItem, Fence::NO_FENCE);
-        processNextBufferLocked(useNextTransaction);
+        acquireNextBufferLocked(transaction);
         return;
     }
 
@@ -455,6 +529,7 @@ void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
 
     // Ensure BLASTBufferQueue stays alive until we receive the transaction complete callback.
     incStrong((void*)transactionCallbackThunk);
+    incStrong((void*)transactionCommittedCallbackThunk);
 
     const bool sizeHasChanged = mRequestedSize != mSize;
     mSize = mRequestedSize;
@@ -475,6 +550,7 @@ void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
     t->setAcquireFence(mSurfaceControl,
                        bufferItem.mFence ? new Fence(bufferItem.mFence->dup()) : Fence::NO_FENCE);
     t->addTransactionCompletedCallback(transactionCallbackThunk, static_cast<void*>(this));
+    t->addTransactionCommittedCallback(transactionCommittedCallbackThunk, static_cast<void*>(this));
     mSurfaceControlsWithPendingCallback.push(mSurfaceControl);
 
     if (updateDestinationFrame) {
@@ -527,7 +603,7 @@ void BLASTBufferQueue::processNextBufferLocked(bool useNextTransaction) {
         t->setApplyToken(mApplyToken).apply();
     }
 
-    BQA_LOGV("processNextBufferLocked size=%dx%d mFrameNumber=%" PRIu64
+    BQA_LOGV("acquireNextBufferLocked size=%dx%d mFrameNumber=%" PRIu64
              " applyTransaction=%s mTimestamp=%" PRId64 "%s mPendingTransactions.size=%d"
              " graphicBufferId=%" PRIu64 "%s transform=%d",
              mSize.width, mSize.height, bufferItem.mFrameNumber, boolToString(applyTransaction),
@@ -543,17 +619,44 @@ Rect BLASTBufferQueue::computeCrop(const BufferItem& item) {
     return item.mCrop;
 }
 
+void BLASTBufferQueue::acquireAndReleaseBuffer() {
+    BufferItem bufferItem;
+    mBufferItemConsumer->acquireBuffer(&bufferItem, 0 /* expectedPresent */, false);
+    mBufferItemConsumer->releaseBuffer(bufferItem, Fence::NO_FENCE);
+    mNumFrameAvailable--;
+}
+
 void BLASTBufferQueue::onFrameAvailable(const BufferItem& item) {
     ATRACE_CALL();
     std::unique_lock _lock{mMutex};
 
     const bool nextTransactionSet = mNextTransaction != nullptr;
+    BQA_LOGV("onFrameAvailable-start nextTransactionSet=%s", boolToString(nextTransactionSet));
     if (nextTransactionSet) {
-        while (mNumFrameAvailable > 0 || maxBuffersAcquired(false /* includeExtraAcquire */)) {
-            BQA_LOGV("waiting in onFrameAvailable...");
+        if (mWaitForTransactionCallback) {
+            // We are waiting on a previous sync's transaction callback so allow another sync
+            // transaction to proceed.
+            //
+            // We need to first flush out the transactions that were in between the two syncs.
+            // We do this by merging them into mNextTransaction so any buffer merging will get
+            // a release callback invoked. The release callback will be async so we need to wait
+            // on max acquired to make sure we have the capacity to acquire another buffer.
+            if (maxBuffersAcquired(false /* includeExtraAcquire */)) {
+                BQA_LOGD("waiting to flush shadow queue...");
+                mCallbackCV.wait(_lock);
+            }
+            while (mNumFrameAvailable > 0) {
+                // flush out the shadow queue
+                acquireAndReleaseBuffer();
+            }
+        }
+
+        while (maxBuffersAcquired(false /* includeExtraAcquire */)) {
+            BQA_LOGD("waiting for free buffer.");
             mCallbackCV.wait(_lock);
         }
     }
+
     // add to shadow queue
     mNumFrameAvailable++;
     ATRACE_INT(mQueuedBufferTrace.c_str(),
@@ -561,7 +664,14 @@ void BLASTBufferQueue::onFrameAvailable(const BufferItem& item) {
 
     BQA_LOGV("onFrameAvailable framenumber=%" PRIu64 " nextTransactionSet=%s", item.mFrameNumber,
              boolToString(nextTransactionSet));
-    processNextBufferLocked(nextTransactionSet /* useNextTransaction */);
+
+    if (nextTransactionSet) {
+        acquireNextBufferLocked(std::move(mNextTransaction));
+        mNextTransaction = nullptr;
+        mWaitForTransactionCallback = true;
+    } else if (!mWaitForTransactionCallback) {
+        acquireNextBufferLocked(std::nullopt);
+    }
 }
 
 void BLASTBufferQueue::onFrameReplaced(const BufferItem& item) {