Revert of Fixes for SkRWBuffer (patchset #5 id:80001 of https://codereview.chromium...

Reason for revert:
Making MSAN and TSAN rather unhappy.

https://build.chromium.org/p/client.skia/builders/Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Debug-MSAN/builds/1586

https://build.chromium.org/p/client.skia/builders/Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-TSAN/builds/5922

Original issue's description:
> Fixes for SkRWBuffer
>
> Do not call SkBufferHead::validate in SkROBuffer's destructor, which
> may be called in a separate thread from SkRWBuffer::append. validate()
> reads SkBufferBlock::fUsed, and append() writes to it, resulting in
> a data race.
>
> Update some comments to be more clear about how it is safe to use
> these classes across threads.
>
> Test the readers in separate threads.
>
> In addition, make sure it is safe to create a reader even when no
> data has been appended. Add tests for this case.
>
> Mark a parameter to SkBufferHead::validate() as const, reflecting
> its use.
>
> BUG=chromium:601578
> GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1871953002
>
> Committed: https://skia.googlesource.com/skia/+/d06920a29fe11c68bde2b93948ec99f277bb8459

TBR=mtklein@google.com,reed@google.com,scroggo@google.com
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:601578

Review URL: https://codereview.chromium.org/1882853004

diff --git a/include/core/SkRWBuffer.h b/include/core/SkRWBuffer.h
index ff80776..d054e0a 100644 (file)
--- a/include/core/SkRWBuffer.h
+++ b/include/core/SkRWBuffer.h
@@ -67,9 +67,8 @@ private:
 
 /**
  *  Accumulates bytes of memory that are "appended" to it, growing internal storage as needed.
- *  The growth is done such that at any time in the writer's thread, an RBuffer or StreamAsset
- *  can be snapped off (and safely passed to another thread). The RBuffer/StreamAsset snapshot
- *  can see the previously stored bytes, but will be unaware of any future writes.
+ *  The growth is done such that at any time, a RBuffer or StreamAsset can be snapped off, which
+ *  can see the previously stored bytes, but which will be unaware of any future writes.
  */
 class SK_API SkRWBuffer {
 public:

diff --git a/src/core/SkRWBuffer.cpp b/src/core/SkRWBuffer.cpp
index bbf88dd..f0b565e 100644 (file)
--- a/src/core/SkRWBuffer.cpp
+++ b/src/core/SkRWBuffer.cpp
@@ -42,8 +42,6 @@ struct SkBufferBlock {
         return amount;
     }
 
-    // Do not call in the reader thread, since the writer may be updating fUsed.
-    // (The assertion is still true, but TSAN still may complain about its raciness.)
     void validate() const {
 #ifdef SK_DEBUG
         SkASSERT(fCapacity > 0);
@@ -96,7 +94,7 @@ struct SkBufferHead {
         }
     }
 
-    void validate(size_t minUsed, const SkBufferBlock* tail = nullptr) const {
+    void validate(size_t minUsed, SkBufferBlock* tail = nullptr) const {
 #ifdef SK_DEBUG
         SkASSERT(fRefCnt > 0);
         size_t totalUsed = 0;
@@ -134,6 +132,7 @@ SkROBuffer::SkROBuffer(const SkBufferHead* head, size_t available)
 
 SkROBuffer::~SkROBuffer() {
     if (fHead) {
+        fHead->validate(fAvailable);
         fHead->unref();
     }
 }
@@ -143,7 +142,7 @@ SkROBuffer::Iter::Iter(const SkROBuffer* buffer) {
 }
 
 void SkROBuffer::Iter::reset(const SkROBuffer* buffer) {
-    if (buffer && buffer->fHead) {
+    if (buffer) {
         fBlock = &buffer->fHead->fBlock;
         fRemaining = buffer->fAvailable;
     } else {

diff --git a/tests/DataRefTest.cpp b/tests/DataRefTest.cpp
index 4bfbff4..002abcb 100644 (file)
--- a/tests/DataRefTest.cpp
+++ b/tests/DataRefTest.cpp
@@ -245,7 +245,7 @@ static void check_abcs(skiatest::Reporter* reporter, const char buffer[], size_t
     }
 }
 
-// stream should contain an integral number of copies of gABC.
+// stream should contains an integral number of copies of gABC.
 static void check_alphabet_stream(skiatest::Reporter* reporter, SkStream* stream) {
     REPORTER_ASSERT(reporter, stream->hasLength());
     size_t size = stream->getLength();
@@ -284,8 +284,6 @@ static void check_alphabet_buffer(skiatest::Reporter* reporter, const SkROBuffer
     check_abcs(reporter, storage.get(), size);
 }
 
-#include "SkTaskGroup.h"
-
 DEF_TEST(RWBuffer, reporter) {
     // Knowing that the default capacity is 4096, choose N large enough so we force it to use
     // multiple buffers internally.
@@ -294,31 +292,17 @@ DEF_TEST(RWBuffer, reporter) {
     SkStream* streams[N];
 
     {
-        SkTaskGroup tasks;
         SkRWBuffer buffer;
         for (int i = 0; i < N; ++i) {
             buffer.append(gABC, 26);
             readers[i] = buffer.newRBufferSnapshot();
             streams[i] = buffer.newStreamSnapshot();
-            REPORTER_ASSERT(reporter, readers[i]->size() == buffer.size());
-            REPORTER_ASSERT(reporter, streams[i]->getLength() == buffer.size());
-
-            tasks.add([reporter, i, &readers, &streams] {
-                REPORTER_ASSERT(reporter, (i + 1) * 26U == readers[i]->size());
-                REPORTER_ASSERT(reporter, streams[i]->getLength() == readers[i]->size());
-                check_alphabet_buffer(reporter, readers[i]);
-                check_alphabet_stream(reporter, streams[i]);
-                REPORTER_ASSERT(reporter, streams[i]->rewind());
-            });
         }
         REPORTER_ASSERT(reporter, N*26 == buffer.size());
-        tasks.wait();
     }
 
-    // Test again, to verify that the snapshots work even after the SkRWBuffer is gone.
     for (int i = 0; i < N; ++i) {
         REPORTER_ASSERT(reporter, (i + 1) * 26U == readers[i]->size());
-        REPORTER_ASSERT(reporter, streams[i]->getLength() == readers[i]->size());
         check_alphabet_buffer(reporter, readers[i]);
         check_alphabet_stream(reporter, streams[i]);
         readers[i]->unref();
@@ -341,27 +325,9 @@ DEF_TEST(RWBuffer_size, r) {
     REPORTER_ASSERT(r, 0 == iter.size());
 }
 
-// Tests that operations (including the destructor) are safe on an SkRWBuffer
-// without any data appended.
+// Tests that it is safe to destruct an SkRWBuffer without appending
+// anything to it.
 DEF_TEST(RWBuffer_noAppend, r) {
     SkRWBuffer buffer;
     REPORTER_ASSERT(r, 0 == buffer.size());
-
-    sk_sp<SkROBuffer> roBuffer = sk_sp<SkROBuffer>(buffer.newRBufferSnapshot());
-    REPORTER_ASSERT(r, roBuffer);
-    if (roBuffer) {
-        REPORTER_ASSERT(r, roBuffer->size() == 0);
-        SkROBuffer::Iter iter(roBuffer.get());
-        REPORTER_ASSERT(r, iter.size() == 0);
-        REPORTER_ASSERT(r, !iter.data());
-        REPORTER_ASSERT(r, !iter.next());
-    }
-
-    SkAutoTDelete<SkStream> stream(buffer.newStreamSnapshot());
-    REPORTER_ASSERT(r, stream);
-    if (stream) {
-        REPORTER_ASSERT(r, stream->hasLength());
-        REPORTER_ASSERT(r, stream->getLength() == 0);
-        REPORTER_ASSERT(r, stream->skip(10) == 0);
-    }
 }