fix multithread related crashes in skpdiff

tools/skpdiff/SkDiffContext.cpp

 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmap.h"
 #include "SkImageDecoder.h"
 #include "SkOSFile.h"
 #include "SkRunnable.h"
 #include "SkStream.h"
 #include "SkTDict.h"
 #include "SkThreadPool.h"
 
 #include "SkDiffContext.h"
-#include "SkImageDiffer.h"
 #include "skpdiff_util.h"
 
 // Truncates the number of points of interests in JSON output to not freeze the parser
 static const int kMaxPOI = 100;
 
 SkDiffContext::SkDiffContext() {
-    fRecords = NULL;
     fDiffers = NULL;
     fDifferCount = 0;
     fThreadCount = SkThreadPool::kThreadPerCore;
 }
 
 SkDiffContext::~SkDiffContext() {
-    // Delete the record linked list
-    DiffRecord* currentRecord = fRecords;
-    while (NULL != currentRecord) {
-        DiffRecord* nextRecord = currentRecord->fNext;
-        SkDELETE(currentRecord);
-        currentRecord = nextRecord;
-    }
-
     if (NULL != fDiffers) {
         SkDELETE_ARRAY(fDiffers);
     }
 }
 
 void SkDiffContext::setDifferenceDir(const SkString& path) {
     if (!path.isEmpty() && sk_mkdir(path.c_str())) {
         fDifferenceDir = path;
     }
 }
@@ skipping 26 matching lines @@
         return b;
     } else {
         return a;
     }
 }
 
 void SkDiffContext::addDiff(const char* baselinePath, const char* testPath) {
     // Load the images at the paths
     SkBitmap baselineBitmap;
     SkBitmap testBitmap;
+    SkAutoMutexAcquire imageLock(fImageMutex);
     if (!SkImageDecoder::DecodeFile(baselinePath, &baselineBitmap)) {
         SkDebugf("Failed to load bitmap \"%s\"\n", baselinePath);
         return;
     }
     if (!SkImageDecoder::DecodeFile(testPath, &testBitmap)) {
         SkDebugf("Failed to load bitmap \"%s\"\n", testPath);
         return;
     }
+    imageLock.release();
 
     // Setup a record for this diff
-    DiffRecord* newRecord = SkNEW(DiffRecord);
+    fRecordMutex.acquire();
+    DiffRecord* newRecord = fRecords.addToHead(DiffRecord());

[mtklein, 2013/11/08 15:06:13]

If you're feeling precise, I think the release can go right after this line.

[djsollen, 2013/11/12 16:40:43]

Done.

     newRecord->fBaselinePath = baselinePath;
     newRecord->fTestPath = testPath;
-    newRecord->fNext = fRecords;
-    fRecords = newRecord;
+    fRecordMutex.release();
 
     // compute the common name
     SkString baseName = SkOSPath::SkBasename(baselinePath);
     SkString testName = SkOSPath::SkBasename(testPath);
     newRecord->fCommonName = get_common_prefix(baseName, testName);
 
     bool alphaMaskPending = false;
     bool alphaMaskCreated = false;
 
     // Perform each diff
     for (int differIndex = 0; differIndex < fDifferCount; differIndex++) {
         SkImageDiffer* differ = fDiffers[differIndex];
-        // TODO only enable for one differ
+        // only enable for one differ
         if (!alphaMaskCreated && !fDifferenceDir.isEmpty()) {
             alphaMaskPending = differ->enablePOIAlphaMask();

[mtklein, 2013/11/08 15:06:13]

Can you eliminate enablePOIAlphaMask?  Make it part of diff?  As written, not
threadsafe.

[djsollen, 2013/11/12 16:40:43]

Done.

         }
-        int diffID = differ->queueDiff(&baselineBitmap, &testBitmap);
-        if (diffID >= 0) {
 
-            // Copy the results into data for this record
-            DiffData& diffData = newRecord->fDiffs.push_back();
+        // Copy the results into data for this record
+        DiffData& diffData = newRecord->fDiffs.push_back();
+
+        if (differ->diff(&baselineBitmap, &testBitmap, &diffData.fResult)) {
 
             diffData.fDiffName = differ->getName();
-            diffData.fResult = differ->getResult(diffID);
-
-            int poiCount = differ->getPointsOfInterestCount(diffID);
-            SkIPoint* poi = differ->getPointsOfInterest(diffID);
-            diffData.fPointsOfInterest.append(poiCount, poi);
 
             if (alphaMaskPending
-                    && SkImageDiffer::RESULT_CORRECT != diffData.fResult
-                    && newRecord->fDifferencePath.isEmpty()) {
+                    && SkImageDiffer::RESULT_CORRECT != diffData.fResult.result
+                    && !newRecord->fCommonName.isEmpty()) {
                 newRecord->fDifferencePath = SkOSPath::SkPathJoin(fDifferenceDir.c_str(),
                                                                   newRecord->fCommonName.c_str());
 
                 // compute the image diff and output it
-                SkBitmap* alphaMask = differ->getPointsOfInterestAlphaMask(diffID);
+                SkASSERT(!diffData.fResult.poiAlphaMask.empty());
                 SkBitmap copy;
-                alphaMask->copyTo(&copy, SkBitmap::kARGB_8888_Config);
+                diffData.fResult.poiAlphaMask.copyTo(&copy, SkBitmap::kARGB_8888_Config);
                 SkImageEncoder::EncodeFile(newRecord->fDifferencePath.c_str(), copy,
                                            SkImageEncoder::kPNG_Type, 100);
+
+                // cleanup the existing bitmap to free up resources;
+                diffData.fResult.poiAlphaMask.reset();
             }
 
             if (alphaMaskPending) {
                 alphaMaskPending = false;
                 alphaMaskCreated = true;
             }
-
-            // Because we are doing everything synchronously for now, we are done with the diff
-            // after reading it.
-            differ->deleteDiff(diffID);
+        } else {
+            // if the diff failed the remove its entry from the list
+            newRecord->fDiffs.pop_back();
         }
     }
-
-    // if we get a difference and we want the alpha mask then compute it here.
 }
 
 class SkThreadedDiff : public SkRunnable {
 public:
     SkThreadedDiff() : fDiffContext(NULL) { }
 
     void setup(SkDiffContext* diffContext, const SkString& baselinePath, const SkString& testPath) {
         fDiffContext = diffContext;
         fBaselinePath = baselinePath;
         fTestPath = testPath;
@@ skipping 69 matching lines @@
 
     for (int x = 0; x < baselineEntries.count(); x++) {
         runnableDiffs[x].setup(this, baselineEntries[x], testEntries[x]);
         threadPool.add(&runnableDiffs[x]);
     }
 
     threadPool.wait();
 }
 
 void SkDiffContext::outputRecords(SkWStream& stream, bool useJSONP) {
-    DiffRecord* currentRecord = fRecords;
+    SkTLList<DiffRecord>::Iter iter(fRecords, SkTLList<DiffRecord>::Iter::kHead_IterStart);
+    DiffRecord* currentRecord = iter.get();
+
     if (useJSONP) {
         stream.writeText("var SkPDiffRecords = {\n");
     } else {
         stream.writeText("{\n");
     }
     stream.writeText("    \"records\": [\n");
     while (NULL != currentRecord) {
         stream.writeText("        {\n");
 
             SkString differenceAbsPath = get_absolute_path(currentRecord->fDifferencePath);
@@ skipping 19 matching lines @@
             stream.writeText("            \"diffs\": [\n");
             for (int diffIndex = 0; diffIndex < currentRecord->fDiffs.count(); diffIndex++) {
                 DiffData& data = currentRecord->fDiffs[diffIndex];
                 stream.writeText("                {\n");
 
                     stream.writeText("                    \"differName\": \"");
                     stream.writeText(data.fDiffName);
                     stream.writeText("\",\n");
 
                     stream.writeText("                    \"result\": ");
-                    stream.writeScalarAsText((SkScalar)data.fResult);
+                    stream.writeScalarAsText((SkScalar)data.fResult.result);
                     stream.writeText(",\n");
 
-                    stream.writeText("                    \"pointsOfInterest\": [\n");
-                    for (int poiIndex = 0; poiIndex < data.fPointsOfInterest.count() &&
-                                           poiIndex < kMaxPOI; poiIndex++) {
-                        SkIPoint poi = data.fPointsOfInterest[poiIndex];
-                        stream.writeText("                        [");
-                        stream.writeDecAsText(poi.x());
-                        stream.writeText(",");
-                        stream.writeDecAsText(poi.y());
-                        stream.writeText("]");
+                    stream.writeText("                    \"pointsOfInterest\": ");
+                    stream.writeDecAsText(data.fResult.poiCount);
+                    stream.writeText("\n");
 
-                        // JSON does not allow trailing commas
-                        if (poiIndex + 1 < data.fPointsOfInterest.count() &&
-                            poiIndex + 1 < kMaxPOI) {
-                            stream.writeText(",");
-                        }
-                        stream.writeText("\n");
-                    }
-                    stream.writeText("                    ]\n");
                 stream.writeText("                }");
 
                 // JSON does not allow trailing commas
                 if (diffIndex + 1 < currentRecord->fDiffs.count()) {
                     stream.writeText(",");
                 }
                 stream.writeText("                \n");
             }
             stream.writeText("            ]\n");
 
         stream.writeText("        }");
 
+        currentRecord = iter.next();
+
         // JSON does not allow trailing commas
-        if (NULL != currentRecord->fNext) {
+        if (NULL != currentRecord) {
             stream.writeText(",");
         }
         stream.writeText("\n");
-        currentRecord = currentRecord->fNext;
     }
     stream.writeText("    ]\n");
     if (useJSONP) {
         stream.writeText("};\n");
     } else {
         stream.writeText("}\n");
     }
 }
 
 void SkDiffContext::outputCsv(SkWStream& stream) {
     SkTDict<int> columns(2);
     int cntColumns = 0;
 
     stream.writeText("key");
 
-    DiffRecord* currentRecord = fRecords;
+    SkTLList<DiffRecord>::Iter iter(fRecords, SkTLList<DiffRecord>::Iter::kHead_IterStart);
+    DiffRecord* currentRecord = iter.get();
 
     // Write CSV header and create a dictionary of all columns.
     while (NULL != currentRecord) {
         for (int diffIndex = 0; diffIndex < currentRecord->fDiffs.count(); diffIndex++) {
             DiffData& data = currentRecord->fDiffs[diffIndex];
             if (!columns.find(data.fDiffName)) {
                 columns.set(data.fDiffName, cntColumns);
                 stream.writeText(", ");
                 stream.writeText(data.fDiffName);
                 cntColumns++;
             }
         }
-        currentRecord = currentRecord->fNext;
+        currentRecord = iter.next();
     }
     stream.writeText("\n");
 
     double values[100];
     SkASSERT(cntColumns < 100);  // Make the array larger, if we ever have so many diff types.
 
-    currentRecord = fRecords;
+    SkTLList<DiffRecord>::Iter iter2(fRecords, SkTLList<DiffRecord>::Iter::kHead_IterStart);
+    currentRecord = iter2.get();
     while (NULL != currentRecord) {
         for (int i = 0; i < cntColumns; i++) {
             values[i] = -1;
         }
 
         for (int diffIndex = 0; diffIndex < currentRecord->fDiffs.count(); diffIndex++) {
             DiffData& data = currentRecord->fDiffs[diffIndex];
             int index = -1;
             SkAssertResult(columns.find(data.fDiffName, &index));
             SkASSERT(index >= 0 && index < cntColumns);
-            values[index] = data.fResult;
+            values[index] = data.fResult.result;
         }
 
         const char* filename = currentRecord->fBaselinePath.c_str() +
                 strlen(currentRecord->fBaselinePath.c_str()) - 1;
         while (filename > currentRecord->fBaselinePath.c_str() && *(filename - 1) != '/') {
             filename--;
         }
 
         stream.writeText(filename);
 
         for (int i = 0; i < cntColumns; i++) {
             SkString str;
             str.printf(", %f", values[i]);
             stream.writeText(str.c_str());
         }
         stream.writeText("\n");
 
-        currentRecord = currentRecord->fNext;
+        currentRecord = iter2.next();
     }
 }