51e80efd12
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} |
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| DEPS | ||
| libplatform-export.h | ||
| libplatform.h | ||
| v8-tracing.h | ||