Bug 1358697

Description of problem:
common: thread_pool worker queue crash in void *item = wq->_void_dequeue();

Version-Release number of selected component (if applicable):

Red Hat Ceph Storage 1.3.2

ceph-common-0.94.5-14.el7cp.x86_64
librbd1-0.94.5-14.el7cp.x86_64
python-rbd-0.94.5-14.el7cp.x86_64
librados2-0.94.5-14.el7cp.x86_64
python-rados-0.94.5-14.el7cp.x86_64


Core was generated by `/usr/bin/python2 /usr/bin/nova-compute --config-file /etc/nova/nova.conf --conf'.
Program terminated with signal 11, Segmentation fault.
#0  ThreadPool::worker (this=0x726e5a0, wt=0x2d9a4f0) at common/WorkQueue.cc:120
120		void *item = wq->_void_dequeue();

(gdb) bt
#0  ThreadPool::worker (this=0x726e5a0, wt=0x2d9a4f0) at common/WorkQueue.cc:120
#1  0x00007f1e59b614d0 in ThreadPool::WorkThread::entry (this=<optimized out>) at common/WorkQueue.h:318
#2  0x00007f1ef0abedc5 in start_thread (arg=0x7f1e599fa700) at pthread_create.c:308
#3  0x00007f1ef00e31cd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:113

(gdb) l
115	      while (tries--) {
116		last_work_queue++;
117		last_work_queue %= work_queues.size();
118		wq = work_queues[last_work_queue];
119		
120		void *item = wq->_void_dequeue();
121		if (item) {
122		  processing++;
123		  ldout(cct,12) << "worker wq " << wq->name << " start processing " << item
124				<< " (" << processing << " active)" << dendl;

(gdb) p wq
$2 = (ThreadPool::WorkQueue_ *) 0x0

It looks like 'wq' was NULL and when it was dereferenced (dereferencing a NULL pointer) in line number 120 it got segfault.

120		void *item = wq->_void_dequeue();