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Commit 20006dc3 authored by Vishnu Nair's avatar Vishnu Nair
Browse files

Avoid capturing always on tracing when generating layers trace 

When we encounter unexpected states, we write the always on
transaction traces to disk so we can investigate and fix these
issues in the field. The states also occur when we generate layers
trace since we use the same logic to replay back the transactions.
In this case we want to avoid writing the trace to disk. This is only
an issue with the perfetto backend since it converts the traces
in process.

Test: presubmit
Fixes: 316896588
Change-Id: I8729328c556f5c0575ac8879d51529cc51259bac
parent a0292284

services/surfaceflinger/Tracing/TransactionTracing.h

+12 −2
Original line number Diff line number Diff line
@@ -218,6 +218,13 @@ class TransactionTraceWriter : public Singleton<TransactionTraceWriter> { 
    friend class Singleton<TransactionTracing>;

    std::function<void(const std::string& prefix, bool overwrite)> mWriterFunction =

            [](const std::string&, bool) {};

    std::atomic<bool> mEnabled{true};



    void doInvoke(const std::string& filename, bool overwrite) {

        if (mEnabled) {

            mWriterFunction(filename, overwrite);

        }

    };



public:

    void setWriterFunction(
@@ -225,12 +232,15 @@ public: 
        mWriterFunction = std::move(function);

    }

    void invoke(const std::string& prefix, bool overwrite) {

        mWriterFunction(TransactionTracing::getFilePath(prefix), overwrite);

        doInvoke(TransactionTracing::getFilePath(prefix), overwrite);

    }

    /* pass in a complete file path for testing */

    void invokeForTest(const std::string& filename, bool overwrite) {

        mWriterFunction(filename, overwrite);

        doInvoke(filename, overwrite);

    }

    /* hacky way to avoid generating traces when converting transaction trace to layers trace. */

    void disable() { mEnabled.store(false); }

    void enable() { mEnabled.store(true); }

};



} // namespace android

services/surfaceflinger/Tracing/tools/LayerTraceGenerator.cpp

+15 −0
Original line number Diff line number Diff line
@@ -40,9 +40,24 @@ 
namespace android {

using namespace ftl::flag_operators;



namespace {

class ScopedTraceDisabler {

public:

    ScopedTraceDisabler() { TransactionTraceWriter::getInstance().disable(); }

    ~ScopedTraceDisabler() { TransactionTraceWriter::getInstance().enable(); }

};

} // namespace



bool LayerTraceGenerator::generate(const perfetto::protos::TransactionTraceFile& traceFile,

                                   std::uint32_t traceFlags, LayerTracing& layerTracing,

                                   bool onlyLastEntry) {

    // We are generating the layers trace by replaying back a set of transactions. If the

    // transactions have unexpected states, we may generate a transaction trace to debug

    // the unexpected state. This is silly. So we disable it by poking the

    // TransactionTraceWriter. This is really a hack since we should manage our depenecies a

    // little better.

    ScopedTraceDisabler fatalErrorTraceDisabler;



    if (traceFile.entry_size() == 0) {

        ALOGD("Trace file is empty");

        return false;

services/surfaceflinger/tests/unittests/TransactionTraceWriterTest.cpp

+12 −0
Original line number Diff line number Diff line
@@ -105,4 +105,16 @@ TEST_F(TransactionTraceWriterTest, overwriteOldFile) { 
    verifyTraceFile();

}



// Check we cannot write to file if the trace write is disabled.

TEST_F(TransactionTraceWriterTest, canDisableTraceWriter) {

    TransactionTraceWriter::getInstance().disable();

    TransactionTraceWriter::getInstance().invokeForTest(mFilename, /* overwrite */ true);

    EXPECT_NE(access(mFilename.c_str(), F_OK), 0);



    TransactionTraceWriter::getInstance().enable();

    TransactionTraceWriter::getInstance().invokeForTest(mFilename, /* overwrite */ true);

    EXPECT_EQ(access(mFilename.c_str(), F_OK), 0);

    verifyTraceFile();

}



} // namespace android
 
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