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From Patrick Hunt <ph...@apache.org>
Subject Re: hang in zookeeper_close() in the mt C client
Date Tue, 01 Feb 2011 01:05:52 GMT
Hi Jeremy, that is unusual, is it reproduceable? Do you have details
on the stack for threads other than this thread doing the close?

It would be best if you could create a JIRA for this, the more detail
you could provide the better (full stacks and any log files)
https://issues.apache.org/jira/browse/ZOOKEEPER

Patrick

On Mon, Jan 31, 2011 at 10:26 AM, Jeremy Stribling <strib@nicira.com> wrote:
> I responded to someone off-list about this, but I just wanted to clarify to
> everyone that the part of the backtrace that isn't shown is entirely within
> my application, and zookeeper_close isn't being called from any Zookeeper
> completion thread.
>
> On 01/29/2011 11:23 AM, Jeremy Stribling wrote:
>>
>> Hi everyone,
>>
>> I use the multithreaded ZK C client library (3.3.2), and I'm seeing my
>> application hang, and the only thread in it that's doing anything
>> interesting is this one:
>>
>> Thread 8 (Thread 5644):
>> #0  0x00007f5d7bb5bbe4 in __lll_lock_wait () from /lib/libpthread.so.0
>> #1  0x00007f5d7bb59ad0 in pthread_cond_broadcast@@GLIBC_2.3.2 () from
>> /lib/libpthread.so.0
>> #2  0x00007f5d793628f6 in unlock_completion_list (l=0x32b4d68) at
>> .../zookeeper/src/c/src/mt_adaptor.c:66
>> #3  0x00007f5d79354d4b in free_completions (zh=0x32b4c80,
>> callCompletion=1, reason=-116) at .../zookeeper/src/c/src/zookeeper.c:1069
>> #4  0x00007f5d79355008 in cleanup_bufs (zh=0x32b4c80, callCompletion=1,
>> rc=-116) at .../thirdparty/zookeeper/src/c/src/zookeeper.c:1125
>> #5  0x00007f5d79353200 in destroy (zh=0x32b4c80) at
>> .../thirdparty/zookeeper/src/c/src/zookeeper.c:366
>> #6  0x00007f5d79358e0e in zookeeper_close (zh=0x32b4c80) at
>> .../zookeeper/src/c/src/zookeeper.c:2326
>> #7  0x00007f5d79356d18 in api_epilog (zh=0x32b4c80, rc=0) at
>> .../zookeeper/src/c/src/zookeeper.c:1661
>> #8  0x00007f5d79362f2f in adaptor_finish (zh=0x32b4c80) at
>> .../zookeeper/src/c/src/mt_adaptor.c:205
>> #9  0x00007f5d79358c8c in zookeeper_close (zh=0x32b4c80) at
>> .../zookeeper/src/c/src/zookeeper.c:2297
>> ....
>>
>> I've seen some threads online about how there's a race condition
>> associated with zookeeper_close, where if you app is making a synchronous
>> call at the same time using the closed zk_handle, there could be a hang.
>>  However, my app makes no synchronous calls, and I'm 99% sure that no other
>> thread in my app is making any concurrent call into the library ('thread
>> apply all bt' in gdb doesn't show any other usage of the library, anyway).
>>
>> Has anyone seen this before?  Any leads?  Thanks,
>>
>> Jeremy
>

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