https://issues.apache.org/bugzilla/show_bug.cgi?id=56857
Bug ID: 56857
Summary: Thread safety issue in
ApplicationContextFacade.invokeMethod
Product: Tomcat 7
Version: 7.0.52
Hardware: PC
OS: Linux
Status: NEW
Severity: major
Priority: P2
Component: Catalina
Assignee: dev@tomcat.apache.org
Reporter: vkleinschm...@blackboard.com
Multiple subsequent Thread dumps were exhibiting lots of threads hanging in
HashMap.get() while in RUNNABLE status, and consuming high CPU - a typical
indicator of a thread safety issue with these non-threadsafe Maps.
Thread stacks all as below.
ApplicationContextFacade implements ServletContext, these objects are
singletons per webapp, and get passed around among multiple threads. Their
private member "objectCache" is a HashMap, i.e. not thread safe, but gets
accessed AND modified without any synchronization in invokeMethod().
Suggested remedy: change to a ConcurrentHashMap, which is thread-safe, and
performs much better than synchronizing on every access.
"connector-93: userId=_101_1, sessionId=C9EC1C59DD2244557BC6231A5476000E"
daemon prio=10 tid=0x00007fb1e40cf800 nid=0x7b90 runnable [0x00007fb1e82c3000]
java.lang.Thread.State: RUNNABLE
at java.util.HashMap.get(HashMap.java:326)
at
org.apache.catalina.core.ApplicationContextFacade.invokeMethod(ApplicationContextFacade.java:789)
at
org.apache.catalina.core.ApplicationContextFacade.doPrivileged(ApplicationContextFacade.java:767)
at
org.apache.catalina.core.ApplicationContextFacade.getContextPath(ApplicationContextFacade.java:428)
at
blackboard.portal.servlet.ModuleCustomizationServlet.service(ModuleCustomizationServlet.java:88)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
...
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