Subj : pthread_mutex_lock -> sem_unlink -> pthread_create?
To   : comp.programming.threads
From : usenet
Date : Mon Jun 20 2005 10:43 am

I'm having a strange problem that I haven't been able to find a
reference to on usenet or the web. A program of ours is experiencing
very high load when processing very little network traffic. Attaching
to one of the busy threads consistently gives backtraces like the one
below. I don't understand why pthread_create is being called here. Is
this normal behaviour from pthread_mutex_lock? Hundreds of threads are
being created, according to the output of repeated ps, which clearly
isn't right.

I don't know whether this is a problem with the way we're using
ZThread, a bug in ZThread, or a bug in glibc's pthread, and I'm at a
brick wall now. Can anyone shed any light on this odd situation?

I'm using glibc 2.3.2 on Linux 2.4.26 SMP (2 x HT CPUs).

#0  0x4166da35 in pthread_getconcurrency () from
/lib/i686/libpthread.so.0
#1  0x4166cdb8 in pthread_create () from /lib/i686/libpthread.so.0
#2  0x4166f210 in sem_unlink () from /lib/i686/libpthread.so.0
#3  0x4166bd77 in pthread_mutex_lock () from /lib/i686/libpthread.so.0
#4  0x4025c96c in ZThread::FastLock::acquire() () from
/usr/lib/ipaccess/bsc/lib/libzthread.so
#5  0x40260e60 in ZThread::FastMutex::acquire() () from
/usr/lib/ipaccess/bsc/lib/libzthread.so
#6  0x0829d1e6 in SmartPtr<ByteBuffer,
ZThread::FastMutex>::removeReference() ()
#7  0x0829bf4b in SmartPtr<ByteBuffer, ZThread::FastMutex>::~SmartPtr()
()
#8  0x40727e6b in
TcpConnectionSubServer::readAnyIcomingMessagesPending() ()
   from /usr/lib/ipaccess/bsc/lib/libipa_sockmgnt.so
#9  0x40725bb8 in TcpConnectionSubServer::run() ()
   from /usr/lib/ipaccess/bsc/lib/libipa_sockmgnt.so
#10 0x4026a8a8 in ZThread::Holder<ZThread::Thread>::run() ()
   from /usr/lib/ipaccess/bsc/lib/libzthread.so
#11 0x4026b8a4 in ZThread::ThreadImpl::dispatch(ZThread::ThreadImpl*,
ZThread::ThreadImpl*, ZThread::CountedPtr<ZThread::Runnable> const&) ()
from /usr/lib/ipaccess/bsc/lib/libzthread.so
#12 0x4026d016 in ZThread::Launcher::run() () from
/usr/lib/ipaccess/bsc/lib/libzthread.so
#13 0x4026f058 in _dispatch () from
/usr/lib/ipaccess/bsc/lib/libzthread.so
#14 0x4166b881 in pthread_detach () from /lib/i686/libpthread.so.0

Thanks,
Dan.

.