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Peter Marshall 51e80efd12 [tracing] Fix races in TracingController implementation
The default TracingController (used by d8 and Node) has some concurrency
issues. The new test flushes these out, when a second thread logs trace
events while the main thread calls StopTracing().

- Use an acquire load in UpdateCategoryGroupEnabledFlags() because this
  was racing with GetCategoryGroupEnabled() where a new category is
  added in the slow path. g_category_groups is append-only, but
  reads/writes to g_category_index need to be correctly ordered so that
  new categories are added and only then is the change to the index
  visible. The relaxed load ignored this and caused unsynchronized
  read/write.
- Use a relaxed load in ~ScopedTracer() to access category_group_enabled
  as this previously used a non-atomic operation which caused a race
  with UpdateCategoryGroupEnabledFlag() which does a relaxed store.
- Replace TracingController::mode_ with an atomic bool as read/writes to
  mode_ were not synchronized and caused TSAN errors. It only has two
  states and it doesn't seem like we will extend this so just convert it
  to bool.
- Take the lock around calling trace_object->Initialize in
  AddTraceEvent(), and around trace_buffer_->Flush() in StopTracing().
  These two raced previously as the underlying TraceBufferRingBuffer
  passes out pointers to TraceObjects in a synchronized way, but the
  caller (AddTraceEvent) then writes into the object without
  synchronization. This leads to races when Flush() is called, at which
  time TraceBufferRingBuffer assumes that all the pointers it handed out
  are to valid, initialized TraceObjects - which is not true because
  AddTraceEvent may still be calling Initialize on them. This could be
  the cause of issues in Node.js where the last line of tracing/logging
  sometimes gets cut off. This is kind of a band-aid solution - access
  to the TraceObjects handed out by the ring buffer really needs proper
  synchronization which at this point would require redesign. It's quite
  likely we will replace this with Perfetto in the near future so not
  much point investing in this code right now.
- Enable TracingCpuProfiler test which was flaky due to these bugs.

Bug: v8:8821
Change-Id: I141296800c6906ac0e7f3f21dd16d861b07dae62
Reviewed-on: https://chromium-review.googlesource.com/c/1477283
Commit-Queue: Peter Marshall <petermarshall@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ali Ijaz Sheikh <ofrobots@google.com>
Cr-Commit-Position: refs/heads/master@{#59752}
2019-02-21 08:34:16 +00:00
benchmarks [test] Ensure random generator in JSTests does not use float arithmetic 2018-12-17 10:05:08 +00:00
build_overrides [ndk] Change android ndk root for v8 2018-01-11 08:10:33 +00:00
custom_deps [build] Add common directory for custom deps 2018-06-08 19:23:02 +00:00
docs [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
gni Reland^2 "[build] disable C++ optimization for mksnapshot code." 2019-02-15 14:44:29 +00:00
include [tracing] Fix races in TracingController implementation 2019-02-21 08:34:16 +00:00
infra [v8] define linux64 gc stress trybot in src side 2019-02-20 15:10:23 +00:00
samples Add a sample that uses the JS API to create wasm 2018-06-07 23:43:38 +00:00
src [tracing] Fix races in TracingController implementation 2019-02-21 08:34:16 +00:00
test [tracing] Fix races in TracingController implementation 2019-02-21 08:34:16 +00:00
testing Remove dummy files created for rolling googletest. 2018-03-27 05:55:56 +00:00
third_party [array] Eagerly copy elements into a FixedArray for sorting 2019-02-18 11:02:17 +00:00
tools [cleanup] Remove obsolete representations. 2019-02-21 06:07:06 +00:00
.clang-format [clang-format] Don't derive pointer alignment 2017-01-17 09:28:19 +00:00
.clang-tidy [tool] Remove unfixed clang-tidy warnings to ease use. 2018-10-26 07:40:32 +00:00
.editorconfig Add .editorconfig 2017-07-28 13:39:24 +00:00
.git-blame-ignore-revs [build] Add DEPS formatting to hyper-blame 2017-10-09 14:08:45 +00:00
.gitattributes .gitattributes: Mark minified emscripten js files as -diff 2018-09-19 16:27:10 +00:00
.gitignore Revert "[build] Port "Add patched eu-strip in third_party"" 2019-01-31 16:44:20 +00:00
.gn [test] Remove obsolete test262 archive extract 2018-03-28 13:52:15 +00:00
.vpython [tools] Correctly identify and report test crashes and infra failures 2018-10-30 15:05:40 +00:00
.ycm_extra_conf.py [ycm] Switch from gnu++11 to gnu++14 2017-11-27 07:48:21 +00:00
AUTHORS Preparing v8 to use with python3 /tools 2019-02-19 09:12:07 +00:00
BUILD.gn [torque] Extract compiler into separate function for easier reusability 2019-02-20 06:17:07 +00:00
ChangeLog [release] Merge ChangeLog back to master 2018-12-07 15:41:59 +00:00
CODE_OF_CONDUCT.md Explicitly state that the Chromium Code of Conduct also applies to V8 2016-03-02 09:51:24 +00:00
codereview.settings Make Gerrit the default code review for V8 2017-06-30 17:37:37 +00:00
DEPS Revert "Roll ICU to 07e7295d from 960f195" 2019-02-20 15:17:45 +00:00
LICENSE Add antlr4 runtime library to support Torque 2018-04-10 10:01:01 +00:00
LICENSE.fdlibm Add LICENSE.fdlibm for all the fdlibm imported sources. 2016-06-09 07:17:03 +00:00
LICENSE.strongtalk Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.v8 Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
LICENSE.valgrind Add LICENSE.v8, LICENSE.strongtalk and LICENSE.valgrind to the v8 2011-02-03 07:10:06 +00:00
OWNERS Reduce wasm OWNERS to current team members 2018-10-15 14:47:49 +00:00
PRESUBMIT.py Revert "[torque] Temporarily disable torque format check to pass presubmit" 2019-02-20 14:07:17 +00:00
README.md [Docs] Removed unused docs because they are moved to GitHub 2015-11-19 10:23:30 +00:00
snapshot_toolchain.gni Reland "Add Windows ARM64 ABI support to V8" 2018-10-24 19:46:36 +00:00
WATCHLISTS Update WATCHLIST wrt yangguo 2018-11-23 08:29:12 +00:00

V8 JavaScript Engine

V8 is Google's open source JavaScript engine.

V8 implements ECMAScript as specified in ECMA-262.

V8 is written in C++ and is used in Google Chrome, the open source browser from Google.

V8 can run standalone, or can be embedded into any C++ application.

V8 Project page: https://github.com/v8/v8/wiki

Getting the Code

Checkout depot tools, and run

    fetch v8

This will checkout V8 into the directory v8 and fetch all of its dependencies. To stay up to date, run

    git pull origin
    gclient sync

For fetching all branches, add the following into your remote configuration in .git/config:

    fetch = +refs/branch-heads/*:refs/remotes/branch-heads/*
    fetch = +refs/tags/*:refs/tags/*

Contributing

Please follow the instructions mentioned on the V8 wiki.