Adding System.out.printlns causes tsan to miss a race?

[Jiri Daněk]

On Sun, Jul 21, 2019 at 10:35 AM Jiri Daněk <jdanek at redhat.com> wrote:

> I compiled jdk-tsan with gcc9, because I had issues compiling with clang_8
> on nixOS. Does that make the test above invalid? I presume I could use
> ubuntu in docker, if asked.
>

Managed to compile with clang_8. With the VERBOSE=true, I get the sanitizer
warning in what feels about 1 in 10 runs. I don't have the gcc9 build any
more to compare, there I never saw warning with VERBOSE=true, but I did not
run it many times and I did not try running in a loop.

One of the lucky runs looks like this

$ build/linux-x86_64-server-release/jdk/bin/java -XX:+ThreadSanitizer
-classpath /home/jdanek/repos/java-sanitizer/out/production/java-sanitizer/
Main
Hello World!
pes
pes
pes
pes
pes
7
pes
==================
WARNING: ThreadSanitizer: data race (pid=22615)
  Read of size 4 at 0x00066390da34 by thread T14:
    #0 Main.lambda$main$0(LMain$1;)V Main.java:13
    #1 Main$$Lambda$36.run()V ??
    #2 java.lang.Thread.run()V Thread.java:835
    #3 (Generated Stub) <null>

  Previous write of size 4 at 0x00066390da34 by thread T1:
    #0 Main.main([Ljava/lang/String;)V Main.java:22
    #1 (Generated Stub) <null>

  Thread T14 (tid=22631, running) created by thread T1 at:
    #0 pthread_create ??:? (java+0x42c5d6)
    #1 os::create_thread(Thread*, os::ThreadType, unsigned long)
/home/jdanek/repos/jdk-tsan/src/hotspot/os/linux/os_linux.cpp:774
(libjvm.so+0xb2683d)
    #2 java.lang.Thread.start()V Thread.java:804
    #3 Main.main([Ljava/lang/String;)V Main.java:19
    #4 (Generated Stub) <null>

  Thread T1 (tid=22617, running) created by main thread at:
    #0 pthread_create ??:? (java+0x42c5d6)
    #1 CallJavaMainInNewThread
/home/jdanek/repos/jdk-tsan/src/java.base/unix/native/libjli/java_md_solinux.c:769
(libjli.so+0x9cba)

SUMMARY: ThreadSanitizer: data race Main.java:13 in
Main.lambda$main$0(LMain$1;)V
==================
7
pes
pes
ThreadSanitizer: reported 1 warnings
ThreadSanitizer: reported 1 warnings
-- 
Mit freundlichen Grüßen / Kind regards
Jiri Daněk