Introduce a dependency monitor for fences

This allows for userspace logging for a buffer and read/write dependencies on the buffer.

Hook up SF to the dependency monitor.

Right now this _does_ emit logs in SF when the primary display is powered down, which is likely indicative of SF being sloppy about release fences in situations where tearing won't be noticeable, but I did verify that manually making screenshotting forget to merge GPU work into a layer's release fence, which has been one way SF's torn the screen, triggers logcat, which is ultimately what we want.

Bug: 360932099
Flag: com.android.graphics.surfaceflinger.flags.monitor_buffer_fences
Test: manually remove screenshot fence handling and check logs

Change-Id: Ica391dfa8a4f2924bb72664b9d9399e4ad9e1747

1 files changed, 6 insertions, 0 deletions

diff --git a/services/surfaceflinger/SurfaceFlinger.cpp b/services/surfaceflinger/SurfaceFlinger.cpp
index 780b897aae..14ec41fded 100644
--- a/services/surfaceflinger/SurfaceFlinger.cpp
+++ b/services/surfaceflinger/SurfaceFlinger.cpp
@@ -5088,6 +5088,12 @@ status_t SurfaceFlinger::setTransactionState(TransactionState&& transactionState
                                                      layerName.c_str(), transactionState.getId());
             if (resolvedState.externalTexture) {
                 resolvedState.state.bufferData->buffer = resolvedState.externalTexture->getBuffer();
+                if (FlagManager::getInstance().monitor_buffer_fences()) {
+                    resolvedState.state.bufferData->buffer->getDependencyMonitor()
+                            .addIngress(FenceTime::makeValid(
+                                                resolvedState.state.bufferData->acquireFence),
+                                        "Incoming txn");
+                }
             }
             mBufferCountTracker.increment(resolvedState.layerId);
         }