Hey Tom,
2011/8/15 Tom <tom.robin...@miranda.com>:
> > It's hanging in spirit. Spirit is one of those libraries in boost
> > which need an explicit compile flag to be used safely in
> > multi-threaded builds (-DBOOST_SPIRIT_THREADSAFE)
>
> > You could start with checking that this flag is indeed being used
> > while building Wt ?
>
> > We did discover this when we built for an ARM target and got also a
> > hang in the first call to spirit code.
>
> This is interesting as it sounds like a very similar problem, and it
> really sounded like this could be the sort of thing that will fix
>
> it.
> We checked a few things in this domain:
> * We checked our Wt build.
> We are cross-compiling it with a cmake toolchain file.
> I am now explicitly setting this define although the cmake output
> shows the following:
> -- Looking for include files CMAKE_HAVE_PTHREAD_H
> -- Looking for include files CMAKE_HAVE_PTHREAD_H - found
> -- Looking for pthread_create in pthreads
> -- Looking for pthread_create in pthreads - not found
> -- Looking for pthread_create in pthread
> -- Looking for pthread_create in pthread - found
> ** Enabling multi threading.
>
> For it to output that last line, the CMakeLists file sets
> -DBOOST_SPIRIT_THREADSAFE on the very next line.
That seems right indeed. Some tips on debugging CMake:
- the CMakeCache.txt contains all state and is a place to adjust
things found by CMake. You could check here that the boost libraries
found are correct, etc...
- VERBOSE=1 make will show all commands executed and is useful to see
what compiler / linker flags are effectively used.
> * We checked our boost build.
> We added this define to the boost build itself - incase it was
> building any precompiled headers, found later it isn't though.
> Boost is compiled with threading=multi also.
This would have been my next guess, that is that boost is not properly
built with multi-threading, or, that you are not linking against the
multi-threaded libs if boost was built to have both single-threaded
and multi-threaded libraries.
To verify that a particular boost library has indeed been built
multi-threaded, you can use ldd to see that the library (e.g.
boost_regex) does depend on libpthread.so
> * We checked the build of our app.
> We didn't have this define in the build of our app so we added it. We
> also added -D_REENTRANT as that was being used in the Wt
These are the compile flags needed for Wt:
-D_REENTRANT -DBOOST_SPIRIT_THREADSAFE -DWT_THREADED
(I am not sure if you actually need them using Wt).
> > So, do I get this correctly: in any build so far, you've never been
> > able to Ctrl-C a Wt application to exit cleanly ?
>
> We can Ctrl-C a Wt app built with our previous toolchain - IE. gcc 4.3.4.
> The gcc 4.3.4 toolchain builds work 100% when run.
> It's just that as the new 4.4.4 toolchain builds work after adding
> -fno-inline
> that makes it seem like maybe we were doing something wrong with the old
> toolchain also, but we just got away with it.
>
> >> So I guess the question is now, has anyone ever seen a problem with
> >> Ctrl-C a Wt app, probably using WServer in particular.
>
> > Actually, even if you use WRun() this creates and manipulates a
> > WServer instance. This probably doesn't matter ?
>
> Interesting. I've just tried the hello.C example app that comes with Wt and
> it goes wrong in the exact same way. IE. web browsers can't connect and once
> a web browser attempts a connect, it can no longer be Ctrl-C.
> This is nice as it makes testing a lot simpler. We are building hello.C with
> the following script for simplicity now (included just so you can see what
> we are linking with and the cflags given):
>
> #!/bin/bash
>
> COMP="$CXX"
> IFLAGS="$TOOLCHAIN_CXXFLAGS $DISTRO_CXXFLAGS"
> LFLAGS="$TOOLCHAIN_LDFLAGS $DISTRO_LDFLAGS"
> SOURCE_FILES="hello.C"
> OUT_FILE="wttest"
>
> LIBS="-lgcc -lgcc_eh -lc -lstdc++"
> WTLIBS="-lwt -lwthttp"
> BOOSTLIBS="-lboost_thread -lboost_regex -lboost_signals -lboost_system
> -lboost_date_time -lboost_filesystem -lboost_program_options"
> MISCLIBS="-lz"
> MISC_OPTS="-ggdb -DDEBUG -D_REENTRANT -DBOOST_SPIRIT_THREADSAFE"
>
> ${COMP} ${IFLAGS} ${LFLAGS} ${LIBS} ${WTLIBS} ${BOOSTLIBS} ${MISCLIBS}
> ${MISC_OPTS} -o ${OUT_FILE} ${SOURCE_FILES}
>
>
> Also we are using eglibc as opposed to glibc, incase there is an issue
> there.
>
>
> > This is the stacktrace which hangs within expireSessions() ?
>
> > This stacktrace indicates that expireSessions is waiting to get a
> > session lock. That would be the case if one session is still actively
> > handling a request, or, there is a problem with an update lock.
>
> > In either case, it would be informative to get stacktraces of all
> threads ?
>
> > We've recently identified one problem in expireSessions(), which was
> > patched on July 25th in git trunk as part of patch
> > 45555e5fe1549e80018401b4d2fd3c2ee9ddf125 (those hunks that touch
> > WebSession.C). But this should not explain why it consistently hangs
> > though.
>
> The trace is from running under gdb, hitting ctrl-c (which causes the hang)
> then ctrl-z to get back to gdbs prompt, then running thread apply all bt.
>
> here is a link to the full backtrace for hello.C for all threads after a
> Ctrl-C,
> I have annotated it with notes when the browser is pointed at the server
> and when Ctrl-C is pressed:
> http://pastebin.com/B7MmbTHc
So this still points to spirit. Since the session hangs there, the
server cannot be shutdown cleanly.
So yes, it is another symptom of the same issue.
> http://pastebin.com/BMhAb6a6
Can you try to build Wt without spirit support (Add -DWT_NO_SPIRIT to
CMAKE_CXX_FLAGS in CMakeCache.txt).
This will disable two optional features:
- plural i18n string resolution using C-like expressions
- parsing the user locale from the accept header
But I think it will be a good test to see if then everything else goes right.
Regards,
koen
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