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https://issues.apache.org/jira/browse/AXIS2C-884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12558762#action_12558762
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Bill Mitchell commented on AXIS2C-884:
--------------------------------------
One reason it is difficult to isolate exactly what is happening is that
WindowsXP exhibits different behavior in a multiple CPU environment than it
does in a single CPU environment. In a single CPU environment, using
axis2_options_set_xml_parser_reset to disable the xmlCleanupParser() call on
each service termination may succeed in avoiding the libxml seg faults. This
does not work in the multiple CPU environment, as seen in the crash below.
This crash can happen even when only one service is created and there is no
parser reset call, provided that the service is created in a "transient" thread
that no longer exists when the service is freed.
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=0x0000239c, int nLine=40696612) Line
> 268 + 0x15 bytes C++
msvcr80d.dll!malloc(unsigned int nSize=16809748) Line 154 + 0x15 bytes
C++
libxml2.dll!xmlGetGlobalState() Line 570 C
libxml2.dll!__xmlDefaultSAXHandler() Line 821 + 0x5 bytes C
libxml2.dll!xmlFreeParserCtxt(_xmlParserCtxt * ctxt=0x02ac6b88) Line
1691 + 0xd bytes C
libxml2.dll!xmlFreeTextReader(_xmlTextReader * reader=0x02a81898) Line
2196 + 0xc bytes C
axis2_parser.dll!axis2_libxml2_reader_wrapper_free(axiom_xml_reader *
parser=0x02ade048, const axutil_env * env=0x019cb498) Line 512 + 0x9 bytes
C
axis2_parser.dll!axiom_xml_reader_free(axiom_xml_reader *
parser=0x02ade048, const axutil_env * env=0x019cb498) Line 35 C
axiom.dll!axiom_stax_builder_free(axiom_stax_builder *
om_builder=0x02b07938, const axutil_env * env=0x019cb498) Line 885 C
axiom.dll!axiom_soap_builder_free(axiom_soap_builder *
soap_builder=0x02a875e8, const axutil_env * env=0x019cb498) Line 189 C
axiom.dll!axiom_soap_envelope_free(axiom_soap_envelope *
soap_envelope=0x02a85a58, const axutil_env * env=0x019cb498) Line 168 C
axis2_engine.dll!axis2_msg_ctx_free(axis2_msg_ctx * msg_ctx=0x02aa5e18,
const axutil_env * env=0x019cb498) Line 374 C
axis2_engine.dll!axis2_op_ctx_free(axis2_op_ctx * op_ctx=0x02aea0a0,
const axutil_env * env=0x019cb498) Line 165 C
axis2_engine.dll!axis2_op_client_free(axis2_op_client *
op_client=0x02aa3ca8, const axutil_env * env=0x019cb498) Line 615 C
axis2_engine.dll!axis2_svc_client_free(axis2_svc_client *
svc_client=0x019f5028, const axutil_env * env=0x019cb498) Line 1287 C
axis2_engine.dll!axis2_stub_free(axis2_stub * stub=0x019cb760, const
axutil_env * env=0x019cb498) Line 129 C
I have not delved into the lower level Windows code to see if the thread
management is doing something special in the multiple CPU case, or if this is
just a race condition that appears more easily in a multi-CPU environment.
Evidently, the only way to avoid the crash is to create Axis initialization and
termination entry points, as suggested above, that can be called by the
application in a persistent thread, or to build enough functionality into
guththila that it can replace libxml.
As it stands today, for the multithreaded application to avoid the crash it
must perform the xmlInitParser() call to libxml2 itself when it starts up,
before multithreaded processing begins, and also set_xml_parser_reset false in
the options of every service client.
> 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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