Jared Cantwell commented on ZOOKEEPER-897:

we are using the 3.3.2 release.  i don't think the patch leaks memory because 
destroy() will eventually get called (by the reentrant call to 
zookeeper_close()), which calls cleanup_bufs() and frees those buffers, right?  
Also, i had a test that reproduced this error, but it was easiest to reproduce 
if i injected artificial sleeps into the zookeeper.c file.  If that's ok, then 
I can submit that.  Otherwise, i'll see if i can devise a test that can 
reproduce it otherwise.

> C Client seg faults during close
> --------------------------------
>                 Key: ZOOKEEPER-897
>                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-897
>             Project: Zookeeper
>          Issue Type: Bug
>          Components: c client
>            Reporter: Jared Cantwell
>            Assignee: Jared Cantwell
>             Fix For: 3.3.2, 3.4.0
>         Attachments: ZOOKEEEPER-897.diff, ZOOKEEPER-897.patch
> 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.

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