SingleFileStore.start() often fails on File.mkdirs() during concurrent cache startup

If multiple caches are started concurrently, SingleFileStore.start() often fails during File.mkdirs(). File.mkdirs() will fail if multiple threads attempt to create the same directories. To improve concurrent reliability of concurrently started caches, this operation should be performed in a synchronized block.

e.g.
[0m[31m17:34:26,994 ERROR [org.jboss.msc.service.fail] (ServerService Thread Pool – 17) MSC000001: Failed to start service jboss.infinispan.web.repl: org.jboss.msc.service.StartException in service jboss.infinispan.web.repl: org.infinispan.commons.CacheException: Unable to invoke method public void org.infinispan.persistence.manager.PersistenceManagerImpl.start() on object of type PersistenceManagerImpl
at org.jboss.as.clustering.msc.AsynchronousService$1.run(AsynchronousService.java:87)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) [rt.jar:1.7.0_25]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) [rt.jar:1.7.0_25]
at java.lang.Thread.run(Thread.java:724) [rt.jar:1.7.0_25]
at org.jboss.threads.JBossThread.run(JBossThread.java:122) [jboss-threads-2.1.1.Final.jar:2.1.1.Final]
Caused by: org.infinispan.commons.CacheException: Unable to invoke method public void org.infinispan.persistence.manager.PersistenceManagerImpl.start() on object of type PersistenceManagerImpl
at org.infinispan.commons.util.ReflectionUtil.invokeAccessibly(ReflectionUtil.java:185)
at org.infinispan.factories.AbstractComponentRegistry$PrioritizedMethod.invoke(AbstractComponentRegistry.java:869)
at org.infinispan.factories.AbstractComponentRegistry.invokeStartMethods(AbstractComponentRegistry.java:638)
at org.infinispan.factories.AbstractComponentRegistry.internalStart(AbstractComponentRegistry.java:627)
at org.infinispan.factories.AbstractComponentRegistry.start(AbstractComponentRegistry.java:530)
at org.infinispan.factories.ComponentRegistry.start(ComponentRegistry.java:216)
at org.infinispan.CacheImpl.start(CacheImpl.java:668)
at org.infinispan.manager.DefaultCacheManager.wireAndStartCache(DefaultCacheManager.java:539)
at org.infinispan.manager.DefaultCacheManager.createCache(DefaultCacheManager.java:502)
at org.infinispan.manager.DefaultCacheManager.getCache(DefaultCacheManager.java:395)
at org.infinispan.manager.DefaultCacheManager.getCache(DefaultCacheManager.java:409)
at org.jboss.as.clustering.infinispan.DefaultCacheContainer.getCache(DefaultCacheContainer.java:103)
at org.jboss.as.clustering.infinispan.DefaultCacheContainer.getCache(DefaultCacheContainer.java:94)
at org.jboss.as.clustering.infinispan.subsystem.CacheService.start(CacheService.java:78)
at org.jboss.as.clustering.msc.AsynchronousService$1.run(AsynchronousService.java:82)
... 4 more
Caused by: org.infinispan.commons.CacheException: Unable to start cache loaders
at org.infinispan.persistence.manager.PersistenceManagerImpl.start(PersistenceManagerImpl.java:154)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) [rt.jar:1.7.0_25]
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57) [rt.jar:1.7.0_25]
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) [rt.jar:1.7.0_25]
at java.lang.reflect.Method.invoke(Method.java:606) [rt.jar:1.7.0_25]
at org.infinispan.commons.util.ReflectionUtil.invokeAccessibly(ReflectionUtil.java:183)
... 18 more
Caused by: org.infinispan.persistence.CacheLoaderException: org.infinispan.commons.CacheConfigurationException: ISPN000238: Directory /home/paul/wildfly/ejb/wildfly/testsuite/integration/clust/target/jbossas-clustering-SYNC-tcp-1/standalone/data/infinispan/web does not exist and cannot be created!
at org.infinispan.persistence.file.SingleFileStore.start(SingleFileStore.java:118)
at org.infinispan.persistence.manager.PersistenceManagerImpl.start(PersistenceManagerImpl.java:121)
... 23 more
Caused by: org.infinispan.commons.CacheConfigurationException: ISPN000238: Directory /home/paul/wildfly/ejb/wildfly/testsuite/integration/clust/target/jbossas-clustering-SYNC-tcp-1/standalone/data/infinispan/web does not exist and cannot be created!
at org.infinispan.persistence.file.SingleFileStore.start(SingleFileStore.java:102)
... 24 more