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  1. ZooKeeper
  2. ZOOKEEPER-897

C Client seg faults during close



    • Bug
    • Status: Closed
    • Major
    • Resolution: Fixed
    • None
    • 3.3.2, 3.4.0
    • c client
    • None
    • Reviewed


      We observed a crash while closing our c client. It was in the do_io() thread that was processing as during the close() call.

      #0 queue_buffer (list=0x6bd4f8, b=0x0, add_to_front=0) at src/zookeeper.c:969
      #1 0x000000000046234e in check_events (zh=0x6bd480, events=<value optimized out>) at src/zookeeper.c:1687
      #2 0x0000000000462d74 in zookeeper_process (zh=0x6bd480, events=2) at src/zookeeper.c:1971
      #3 0x0000000000469c34 in do_io (v=0x6bd480) at src/mt_adaptor.c:311
      #4 0x00007ffff7bc59ca in start_thread () from /lib/libpthread.so.0
      #5 0x00007ffff6f706fd in clone () from /lib/libc.so.6
      #6 0x0000000000000000 in ?? ()

      We tracked down the sequence of events, and the cause is that input_buffer is being freed from a thread other than the do_io thread that relies on it:

      1. do_io() call check_events()
      2. if(events&ZOOKEEPER_READ) branch executes
      3. if (rc > 0) branch executes
      4. if (zh->input_buffer != &zh->primer_buffer) branch executes
      .....in the meantime......
      5. zookeeper_close() called
      6. if (inc_ref_counter(zh,0)!=0) branch executes
      7. cleanup_bufs() is called
      8. input_buffer is freed at the end
      ..... back to check_events().........
      9. queue_events() is called on a NULL buffer.

      I believe the patch is to only call free_completions() in zookeeper_close() and not cleanup_bufs(). The original reason cleanup_bufs() was added was to call any outstanding synhcronous completions, so only free_completions (which is guarded) is needed. I will submit a patch for review with this change.


        1. ZOOKEEPER-897.patch
          0.5 kB
          Jared Cantwell
        2. ZOOKEEEPER-897.diff
          0.4 kB
          Jared Cantwell



            jaredc Jared Cantwell
            jaredc Jared Cantwell
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