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

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 
#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.

This message is automatically generated by JIRA.
You can reply to this email to add a comment to the issue online.

Reply via email to