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https://issues.apache.org/jira/browse/AXIS2C-884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12556569#action_12556569
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Bill Mitchell commented on AXIS2C-884:
--------------------------------------
To isolate what kind of fix might work for the multithreading case, for testing
I commented out the xmlInitParser() and xmlCleanupParser() calls and moved
these into the application threads. If these calls are issued once at the
start of the application and once at the end, all works well. The same is not
true when attempting to use libxml2 serially in multiple threads. In
particular, I tried creating and freeing the stub around each SOAP message, and
performing an xmlInitParser and xmlCleanupParser around each use. Even in the
application where mutex's can ensure that the xmlCleanupParser() completes
before an xmlInitParser() is issued, and the use_counts are maintained under
mutex to avoid race conditions, the first time libxml2 is initialized in a
second thread after being freed in the first thread, the crash in
xmlGetGlobalState reappears. See the traceback below, as well as relevant
trace lines from my application trace.
ntdll.dll!7c918fea()
[Frames below may be incorrect and/or missing, no symbols loaded for
ntdll.dll]
kernel32.dll!7c80e98b()
> msvcr80d.dll!_nh_malloc_dbg(unsigned int nSize=12, int nhFlag=0, int
> nBlockUse=0, const char * szFileName=0x00002220, int nLine=67225284) Line
> 268 + 0x15 bytes C++
msvcr80d.dll!malloc(unsigned int nSize=17792788) Line 154 + 0x15 bytes
C++
libxml2.dll!xmlGetGlobalState() Line 570 C
[EMAIL PROTECTED] : | | | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Initializing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Freeing libxml2
[EMAIL PROTECTED] : | | | | | | | | info: Initializing libxml2
> Seg fault in libxml when svc client torn down in a multithreaded client
> -----------------------------------------------------------------------
>
> Key: AXIS2C-884
> URL: https://issues.apache.org/jira/browse/AXIS2C-884
> Project: Axis2-C
> Issue Type: Bug
> Components: core/deployment
> Affects Versions: Current (Nightly)
> Environment: Windows XP, Visual Studio 2005, libxml 2.6.25 and libxml
> 2.6.30, libcurl
> Reporter: Bill Mitchell
> Attachments: axis2.trace, desc_builder_diff.txt
>
>
> In a multithreaded application, if the stub/svc client is freed in a thread
> different from that used when the svc client was built, libxml crashes. The
> trace below shows the information available from a release build with debug
> information embedded.
> I have verified this is not an effect of combining debug and release C
> runtimes, or different versions of the C runtime. Rebuilding all the libxml
> related dlls with the same runtime as is used for Axis and the client app
> does not solve the problem.
> Interestingly, rebuilding libxml with threads disabled does make the crash go
> away. But the default build of libxml commonly available has native threads
> enabled, and building without thread support may make the library not thread
> safe.
> By adding debug trace statements in the axis2.trace file, I have verified
> that the xml_reader being torn down when the crash happens is the one used to
> read the axis2.xml file when the configuration was first read. (axis2.trace
> file attached.)
> Looking at the code in libxml, it appears that libxml decides to close the
> reader using an internal close routine intended for closing compressed
> channels through zlib. Apparently the C runtime library returns a -1 EOF
> status when closing a file opened for read. The close routine, gzio.c in
> zlib, treats this as an error, and when libxml attempts to report the error
> and determines that it is in a different thread, things really go downhill
> fast. I have not isolated why the EnterCriticalSection call crashes in the
> system, but it does.
> One way to avoid the problem would be to guarantee that the stub/svc client
> is freed in the same thread as created it. In my multithreaded client
> application, though, I work hard to share the stub across threads
> deliberately to reduce the number of distinct service clients and the
> associated demand on the server.
> Windows call traceback at time of crash:
> ntdll.dll!7c918fea()
> [Frames below may be incorrect and/or missing, no symbols loaded for
> ntdll.dll]
> msvcr80.dll!78134d09()
> ntdll.dll!7c910e91()
> ntdll.dll!7c9106eb()
> msvcr80.dll!78134d83()
> ntdll.dll!7c90104b()
> > libxml2.dll!xmlGetGlobalState() Line 570 C
> libxml2.dll!__xmlLastError() Line 709 + 0x5 bytes C
> libxml2.dll!__xmlRaiseError(void (void *, _xmlError *)*
> schannel=0x00000000, void (void *, const char *, <no type>)*
> channel=0x00000000, void * data=0x00000000, void * ctx=0x00000000, void *
> nod=0x00000000, int domain=8, int code=0, xmlErrorLevel level=XML_ERR_ERROR,
> const char * file=0x00000000, int line=0, const char * str1=0x00c5d420, const
> char * str2=0x00000000, const char * str3=0x00000000, int int1=0, int col=0,
> const char * msg=0x00c5d360, ...) Line 452 + 0x5 bytes C
> libxml2.dll!__xmlSimpleError(int domain=8, int code=0, _xmlNode *
> node=0x00000000, const char * msg=0x00c5d360, const char * extra=0x00c5d420)
> Line 657 + 0x2d bytes C
> libxml2.dll!__xmlIOErr(int domain=8, int code=0, const char *
> extra=0x00c5d420) Line 417 + 0x1a bytes C
> libxml2.dll!xmlGzfileClose(void * context=0x03301f80) Line 1155 + 0x10
> bytes C
> libxml2.dll!xmlFreeParserInputBuffer(_xmlParserInputBuffer *
> in=0x03304578) Line 2207 + 0x5 bytes C
> libxml2.dll!xmlTextReaderClose(_xmlTextReader * reader=0x03304760)
> Line 2244 + 0x6 bytes C
> axis2_parser.dll!axis2_libxml2_reader_wrapper_free(axiom_xml_reader *
> parser=0x03301e00, const axutil_env * env=0x031aa150) Line 510 C
> axiom.dll!axiom_stax_builder_free(axiom_stax_builder *
> om_builder=0x03271aa8, const axutil_env * env=0x031aa150) Line 886 C
> axis2_engine.dll!axis2_desc_builder_free(axis2_desc_builder *
> desc_builder=0x03301d58, const axutil_env * env=0x031aa150) Line 141 C
> axis2_engine.dll!axis2_conf_builder_free(axis2_conf_builder *
> conf_builder=0x03301d70, const axutil_env * env=0x031aa150) Line 128 C
> axis2_engine.dll!axis2_dep_engine_free(axis2_dep_engine *
> dep_engine=0x031aa2e8, const axutil_env * env=0x031aa150) Line 380 C
> axis2_engine.dll!axis2_conf_free(axis2_conf * conf=0x0330cad8, const
> axutil_env * env=0x031aa150) Line 328 C
> axis2_engine.dll!axis2_conf_ctx_free(axis2_conf_ctx *
> conf_ctx=0x00000000, const axutil_env * env=0x031aa150) Line 439 C
> axis2_engine.dll!axis2_svc_client_free(axis2_svc_client *
> svc_client=0x031aa1a8, const axutil_env * env=0x031aa150) Line 1303 C
> axis2_engine.dll!axis2_stub_free(axis2_stub * stub=0x031aa198, const
> axutil_env * env=0x031aa150) Line 131 C
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