commit df868baf2abefbb45341530d20a948ffd6b2c304
author Alec Mouri <alecmouri@google.com> Tue Feb 25 16:08:19 2025 -0800
committer Alec Mouri <alecmouri@google.com> Thu Mar 13 15:41:05 2025 -0700
tree e1e4b886b5a03e0dee5f6780ee3a0431af9637db
parent c28b463221a7516fa8e9aa30dfd33f290f635e99

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

libs/ui/GraphicBuffer.cpp

diff --git a/libs/ui/GraphicBuffer.cpp b/libs/ui/GraphicBuffer.cpp
index 18c9a6b..f7c9400 100644
--- a/libs/ui/GraphicBuffer.cpp
+++ b/libs/ui/GraphicBuffer.cpp
@@ -27,6 +27,8 @@
 #include <ui/GraphicBufferMapper.h>
 #include <utils/Trace.h>
 
+#include <string>
+
 namespace android {
 
 // ===========================================================================
@@ -104,6 +106,7 @@
     usage  = 0;
     layerCount = 0;
     handle = nullptr;
+    mDependencyMonitor.setToken(std::to_string(mId));
 }
 
 // deprecated
@@ -155,6 +158,8 @@
         layerCount = request.layerCount;
         usage = request.usage;
         usage_deprecated = int(usage);
+        std::string name = request.requestorName;
+        mDependencyMonitor.setToken(name.append(":").append(std::to_string(mId)));
     }
 }
 
@@ -252,6 +257,7 @@
         usage = inUsage;
         usage_deprecated = int(usage);
         stride = static_cast<int>(outStride);
+        mDependencyMonitor.setToken(requestorName.append(":").append(std::to_string(mId)));
     }
     return err;
 }
@@ -609,6 +615,14 @@
         mBufferMapper.getTransportSize(handle, &mTransportNumFds, &mTransportNumInts);
     }
 
+    std::string name;
+    status_t err = mBufferMapper.getName(handle, &name);
+    if (err != NO_ERROR) {
+        name = "<Unknown>";
+    }
+
+    mDependencyMonitor.setToken(name.append(":").append(std::to_string(mId)));
+
     buffer = static_cast<void const*>(static_cast<uint8_t const*>(buffer) + sizeNeeded);
     size -= sizeNeeded;
     fds += numFds;