QUIC - instrumentation for testing null QuicSpdyStream.

net/quic/quic_http_stream.cc

Index: net/quic/quic_http_stream.cc
diff --git a/net/quic/quic_http_stream.cc b/net/quic/quic_http_stream.cc
index db671f22e925e3313ae37f648a0e7e762eac4f1b..54ce648b7df7aac00a09497cb0405c9da046ff21 100644
--- a/net/quic/quic_http_stream.cc
+++ b/net/quic/quic_http_stream.cc
@@ -556,7 +556,11 @@ int QuicHttpStream::ProcessResponseHeaders(const SpdyHeaderBlock& headers) {
 }
 
 int QuicHttpStream::ReadAvailableData(IOBuffer* buf, int buf_len) {
+  // TODO(rtenneti): Temporary until crbug.com/585591 is solved.
+  stream_->CrashIfInvalid();
   int rv = stream_->Read(buf, buf_len);
+  // TODO(rtenneti): Temporary until crbug.com/585591 is solved.
+  stream_->CrashIfInvalid();

[eroman, 2016/02/11 02:16:33]

Driveby comments:

According to the crash data for that bug, this is going to blow up without
telling us anything new since it will be a null-ptr de-ref (the crash data shows
that the crashes in IsDoneReading are small offsets from 0 [1])

Based on the working theory in the bug, that stream_->Read() is executing code
that ultimately NULL's stream_, I think a better instrumentation would be to see
if QuicHttpStream::ResetStream() has been called. Since that will definitively
confirm that code in Read() is causing a re-entrancy into this QuickHttpStream.

How about before calling stream_->CrashIfInvalid() you assert that ResetStream()
wasn't called? (Are there any other ways to cause stream_ to be NULL-ed?)

Maybe you have a member variable 'int reset_stream_count_ = 0"  which
ResetStream() increments. If that gives us data, you can go a step further and
add a base::Debug::StackTrace which captures the callstack that ResetStream()
was called from.

[1]
https://crash.corp.google.com/browse?q=custom_data.ChromeCrashProto.ptype%3D%...

[ramant (doing other things), 2016/02/11 19:45:46]

Acknowledged.

Thanks Eric. Added more instrumentation. +1 to ResetStream() being called during
Read(). Hopefully, new instrumentation will show the unusual conditions under
which it could happen.

   if (stream_->IsDoneReading()) {
     stream_->SetDelegate(nullptr);
     stream_->OnFinRead();