• Michael Lippautz's avatar
    Reland "cppgc-js: Concurrently process v8::TracedReference" · 2da23bd5
    Michael Lippautz authored
    This is a reland of commit 1f0d7d20
    
    The fix merges concurrent marking tasks when marking in the atomic
    pause. Without the fix, Oilpan markers would continue running
    concurrently, possibly discovering new V8 objects. This violates the
    assumption that the final transitive closure runs on a single thread.
    
    Original change's description:
    > cppgc-js: Concurrently process v8::TracedReference
    >
    > Adds concurrent marking for reaching through v8::TracedReference.
    > Before this CL, a v8::TracedReference would always be processed on the
    > main thread by pushing a callback for each encountered reference.
    >
    > This CL now wires up concurrent handling for such references. In particular:
    > - Global handles are already marked as well and not repurposed during
    >   the same GC cycle.
    > - Since global handles are not repurposed, it is enough to
    >   double-deref to the V8 object, checking for possible null pointers.
    > - The bitmap for global handle flags is mostly non-atomic, with the
    >   markbit being the exception.
    > - Finally, all state is wired up in CppHeap. Concurrent markers keep
    >   their own local worklist while the mutator marker directly pushes to
    >   the worklist owned by V8.
    >
    > Bug: v8:12600
    > Change-Id: Ia67dbd18a57dbcccf4dfb9ccfdb9ee438d27fe71
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3516255
    > Reviewed-by: Omer Katz <omerkatz@chromium.org>
    > Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
    > Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
    > Cr-Commit-Position: refs/heads/main@{#79736}
    
    Bug: v8:12600
    Change-Id: I8545041b2c7b3daf7ecea7e3a100e27534e9b8b5
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3571887Reviewed-by: 's avatarDominik Inführ <dinfuehr@chromium.org>
    Reviewed-by: 's avatarOmer Katz <omerkatz@chromium.org>
    Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
    Cr-Commit-Position: refs/heads/main@{#79919}
    2da23bd5
BUILD.bazel 138 KB