• Leszek Swirski's avatar
    [offthread] Make publish merging and handle fixup atomic · bbc8f787
    Leszek Swirski authored
    Make sure that any GCs required for off-thread heap merging happen
    before any off-thread handle transferring (both transferring using
    OffThreadTransferHandle, and the handles created for the string slot
    fixups). This is to avoid the marker from walking Handle roots that
    point into off-thread pages which the sweeper doesn't see (and can't
    clear mark bits on)
    
    Now, the merging and handle creation is atomic as far as the GC is
    concerned. The merging is done before handle creation to avoid the
    incremental marker from entering off-thread pages, but we ensure that
    the raw objects pointers that point into the off-thread pages (which
    are used for creating the main-thread handles) stay valid until the
    handle creation completes.
    
    Since handle transfer now happens in the middle of publishing, this
    patch also moves the OffThreadTransferHandleStorage ownership over to
    OffThreadHeap. This requires some header juggling to avoid leaking
    OffThreadTransferHandleStorage into the off-thread-isolate header.
    
    Bug: chromium:1086478, chromium:1011762
    Change-Id: Id5e7622d6b5520400a4872c5f6ad396c74b30ca6
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2218058Reviewed-by: 's avatarUlan Degenbaev <ulan@chromium.org>
    Reviewed-by: 's avatarToon Verwaest <verwaest@chromium.org>
    Auto-Submit: Leszek Swirski <leszeks@chromium.org>
    Commit-Queue: Toon Verwaest <verwaest@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#68043}
    bbc8f787
off-thread-heap.cc 11.8 KB