RE: Garbage Collection, Interrupted

Vidar Berg — Thu, 07 Jan 2021 08:46:08 GMT

Hello,

Sorry for the delayed response. I was not aware of this particular bug, but I found the exact same fix implemented on our master branch with a similar comment about the problem with reentry (see snippet below). So it seems like your patch must be a valid fix for this bug.

fds.c on Master

        case FDS_OP_INIT_PROMOTE_SWAP:
        {
            p_op->init.step       = FDS_OP_INIT_TAG_SWAP;

            uint16_t const         gc         = m_gc.cur_page;
            uint32_t const * const p_old_swap = m_swap_page.p_addr;

            // Execute the swap.
            m_swap_page.p_addr = m_pages[gc].p_addr;
            m_pages[gc].p_addr = p_old_swap;

            // Copy the offset from the swap to the new page.
            m_pages[gc].write_offset = m_swap_page.write_offset;
            m_swap_page.write_offset = FDS_PAGE_TAG_SIZE;

            m_pages[gc].page_type = FDS_PAGE_DATA;

            // Promote the old swap page to data, but do this at the end
            // because we can re-enter this function; we must update have
            // updated the page in RAM before that.
            ret = page_tag_write_data(p_old_swap);
        } break;
        ...