[do not merge] Use locks in single-threaded mode

[Zoxc]

Checking performance overhead of doing so.

[rust-highfive]

r? @cramertj

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[Zoxc]

@bors try

[bors]

⌛ Trying commit 628b351 with merge 981f103d1dd1f8a26cc17f17c2a5a295c1c7f554...

[rust-highfive]

The job mingw-check of your PR failed on Travis (raw log). Through arcane magic we have determined that the following fragments from the build log may contain information about the problem.

Click to expand the log.

travis_time:end:0e73b826:start=1554238855868401644,finish=1554238856763566237,duration=895164593
$ git checkout -qf FETCH_HEAD
travis_fold:end:git.checkout

Encrypted environment variables have been removed for security reasons.
See https://docs.travis-ci.com/user/pull-requests/#pull-requests-and-security-restrictions
$ export SCCACHE_BUCKET=rust-lang-ci-sccache2
$ export SCCACHE_REGION=us-west-1
$ export GCP_CACHE_BUCKET=rust-lang-ci-cache
Setting environment variables from .travis.yml
---
travis_time:end:04d44000:start=1554239165773349925,finish=1554239165777949142,duration=4599217
travis_fold:end:after_failure.3
travis_fold:start:after_failure.4
travis_time:start:14de2ccf
$ ln -s . checkout && for CORE in obj/cores/core.*; do EXE=$(echo $CORE | sed 's|obj/cores/core\.[0-9]*\.!checkout!\(.*\)|\1|;y|!|/|'); if [ -f "$EXE" ]; then printf travis_fold":start:crashlog\n\033[31;1m%s\033[0m\n" "$CORE"; gdb --batch -q -c "$CORE" "$EXE" -iex 'set auto-load off' -iex 'dir src/' -iex 'set sysroot .' -ex bt -ex q; echo travis_fold":"end:crashlog; fi; done || true
travis_fold:end:after_failure.4
travis_fold:start:after_failure.5
travis_time:start:17416068
travis_time:start:17416068
$ cat ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers || true
cat: ./obj/build/x86_64-unknown-linux-gnu/native/asan/build/lib/asan/clang_rt.asan-dynamic-i386.vers: No such file or directory
travis_fold:end:after_failure.5
travis_fold:start:after_failure.6
travis_time:start:3335f9a8
$ dmesg | grep -i kill

I'm a bot! I can only do what humans tell me to, so if this was not helpful or you have suggestions for improvements, please ping or otherwise contact @TimNN. (Feature Requests)

[bors]

☀️ Try build successful - checks-travis
Build commit: 981f103d1dd1f8a26cc17f17c2a5a295c1c7f554

[Zoxc]

@rust-timer build 981f103d1dd1f8a26cc17f17c2a5a295c1c7f554

[rust-timer]

Success: Queued 981f103d1dd1f8a26cc17f17c2a5a295c1c7f554 with parent 428943c, comparison URL.

[rust-timer]

Finished benchmarking try commit 981f103d1dd1f8a26cc17f17c2a5a295c1c7f554

[alexcrichton]

I'm gonna close this since I believe we've gathered the data intended