[IMPALA-3946] Hit DCHECK in MemPool::CheckIntegrity()

• Type: Bug
• Status: Resolved
• Priority: Blocker
• Resolution: Fixed
• Affects Version/s: Impala 2.7.0
• Fix Version/s: Impala 2.7.0
• Component/s: Backend
• Labels: crash
• Target Version: Impala 2.7.0
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 03/Aug/16 23:01
• Updated: 11/Aug/16 04:34
• Resolved: 11/Aug/16 04:34

Description

When running the scanner fuzzing, I hit this DCHECK in the mempool integrity check. The issue seems to be connected with making large allocations. Looking at the code, I think there are at least two separate issues that could lead to this being hit with ReturnPartialAllocation() and in FindChunk() if the memory can't be allocated.

bool MemPool::CheckIntegrity(bool current_chunk_empty) {
  DCHECK_EQ(zero_length_region_, MEM_POOL_POISON);

  // Without pooling, there are way too many chunks and this takes too long.
  if (FLAGS_disable_mem_pools) return true;

  // check that current_chunk_idx_ points to the last chunk with allocated data
  DCHECK_LT(current_chunk_idx_, static_cast<int>(chunks_.size()));
  int64_t total_allocated = 0;
  for (int i = 0; i < chunks_.size(); ++i) {
    DCHECK_GT(chunks_[i].size, 0);
    if (i < current_chunk_idx_) {
      DCHECK_GT(chunks_[i].allocated_bytes, 0); <=== HERE
    } else if (i == current_chunk_idx_) {
      if (current_chunk_empty) {
        DCHECK_EQ(chunks_[i].allocated_bytes, 0);
      } else {
        DCHECK_GT(chunks_[i].allocated_bytes, 0);
      }
    } else {
      DCHECK_EQ(chunks_[i].allocated_bytes, 0);
    }
    total_allocated += chunks_[i].allocated_bytes;
  }
  DCHECK_EQ(total_allocated, total_allocated_bytes_);
  return true;
}