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From "Freeman Fang (JIRA)" <j...@apache.org>
Subject [jira] [Resolved] (CXF-4404) atomicity violation bugs because of misusing concurrent collections
Date Fri, 06 Jul 2012 06:23:34 GMT

     [ https://issues.apache.org/jira/browse/CXF-4404?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Freeman Fang resolved CXF-4404.
-------------------------------

       Resolution: Fixed
    Fix Version/s: 2.7.0
                   2.6.2

Apply patch on behalf of Yu Lin with thanks
                
> atomicity violation bugs because of misusing concurrent collections
> -------------------------------------------------------------------
>
>                 Key: CXF-4404
>                 URL: https://issues.apache.org/jira/browse/CXF-4404
>             Project: CXF
>          Issue Type: Bug
>    Affects Versions: 2.6.1
>            Reporter: Yu Lin
>            Assignee: Freeman Fang
>              Labels: patch
>             Fix For: 2.6.2, 2.7.0
>
>         Attachments: cxf-2.6.1.patch
>
>   Original Estimate: 504h
>  Remaining Estimate: 504h
>
> My name is Yu Lin. I'm a Ph.D. student in the CS department at
> UIUC. I'm currently doing research on mining Java concurrent library
> misusages. I found some misusages of ConcurrentHashMap in CXF 2.6.1,
> which may result in potential atomicity violation bugs or harm the
> performance.
> The code below is a snapshot of the code in file
> api/src/main/java/org/apache/cxf/common/util/ASMHelper.java from line
> 306 to 327.
> L306        public synchronized Class<?> defineClass(String name, byte bytes[])
{
> L307            Class<?> ret = defined.get(name.replace('/', '.'));
> L308            if (ret != null) {
> L309                return ret;
> L310            }
> L311            if (name.endsWith("package-info")) {
>                     ...
> L323            }
> L324            
> L325            ret = super.defineClass(name.replace('/', '.'), bytes, 0, bytes.length);
> L326            defined.put(name.replace('/', '.'), ret);
> L327            return ret;
> In the code above, the synchronized key word at line 306 can be
> removed if we use putIfAbsent at line 326. If we remove the
> synchronized without using putIfAbsent, an atomicity violation may
> occur between lines <310 and 326>: Suppose a thread T1 executes line
> 307 and finds out the concurrent hashmap dose not contain the key
> "name.replace('/','.')". Before it gets to execute line 326, another
> thread T2 puts a pair <name.replace('/','.'), v> in the concurrent
> hashmap "defined". Now thread T1 resumes execution and it will
> overwrite the value written by thread T2. Thus, the code no longer
> preserves the "put-if-absent" semantics. However, such atomicity
> violation bug can be eliminated by using putIfAbsent at line 326 (see
> the patch).
> I found some similar misusages in other files:
> In
> api/src/main/java/org/apache/cxf/configuration/spring/AbstractSpringBeanMap.java,
> synchronized key word at line 67 can be removed by using putIfAbsent
> at line 71. Also, atomicity violations may occur when T2 removes key
> "key" from the concurrent hashmap "putStore" before T1 executes line
> 155; or T2 puts a pair <(X)key, v> to "putStore" before T1 executes
> line 158.
> In api/src/main/java/org/apache/cxf/endpoint/ClientImpl.java, an
> atomicity violation may occur when thread T2 removes key
> "THREAD_LOCAL_REQUEST_CONTEXT" from the concurrent hashmap
> "currentRequestContext" before thread T1 executes line 303.
> In api/src/main/java/org/apache/cxf/helpers/HttpHeaderHelper.java, an
> atomicity violation may occur when thread T2 puts a pair <enc, v> to
> concurrent hashmap "encodings" before T1 executes line 127.
> In
> rt/core/src/main/java/org/apache/cxf/bus/osgi/CXFExtensionBundleListener.java,
> an atomicity violation may occur when thread T2 puts a pair
> <bundle.getBundleId(), v> to concurrent hashmap "extensions" before T1
> executes line 93.
> In
> rt/features/clustering/src/main/java/org/apache/cxf/clustering/FailoverTargetSelector.java,
> synchronized key word at line 76 can be removed by using putIfAbsent
> at line 91.
> In
> rt/frontend/jaxrs/src/main/java/org/apache/cxf/jaxrs/model/ClassResourceInfo.java,
> if another thread T2 puts a pair <key, v> into concurrent hashmap
> "subResources" before thread T1 executes line 136, the "cri" in T1
> won't be put into "subResources" at line 136. In this case, the
> "getSubResource" method returns the wrong "cri".
> In
> rt/rs/extensions/providers/src/main/java/org/apache/cxf/jaxrs/provider/json/JSONProvider.java,
> an atomicity violation may occur when thread T2 removes key
> "qname.getNamespaceURI()" from the concurrent hashmap "namespaceMap"
> before thread T1 executes line 405. Another atomicity violation is
> when thread T2 puts a pair <namespace, v> to concurrent hashmap
> "namespaceMap" before T1 executes line 530.
> In
> rt/transports/http-jetty/src/main/java/org/apache/cxf/transport/http_jetty/JettyHTTPServerEngineFactory.java,
> synchronized key word at line 107 can be removed by using putIfAbsent
> at line 118.
> In
> rt/transports/local/src/main/java/org/apache/cxf/transport/local/LocalTransportFactory.java,
> an atomicity violation may occur when thread T2 puts a pair <addr, v>
> to concurrent hashmap "destinations" before T1 executes line 128.

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