[Click] Kernel static objects

[springbo at cs.wisc.edu]

Thanks Eddie,

Exactly what I was looking for!


~Kevin Springborn




> Hi Kevin,
>
> This is what Element static_initialize() and static_cleanup() are for.  Is
> there any way you can change your static objects into static *pointers*,
> which
> being plain old data types should not cause GCC to introduce
> __cxa_atexit/__dso_handle, then initialize the pointers in
> static_initialize()
> and destroy them in static_cleanup()?
>
> Eddie
>
>
> springbo at cs.wisc.edu wrote:
>> Hi,
>>
>>
>>
>> I've run into a couple of problems when using static objects in kernel
>> level code. I'm using the click sources from the dev tree as of two
>> weeks
>> ago, the 2.6.19.2 kernel, gcc v4.1.2 20071124 and a x86_64
>> multi-threaded
>> target.
>>
>>
>>
>> The symbols __cxa_atexit and __dso_handle are undefined when I use
>> static
>> objects in my elements (See the commented paragraph of
>> http://www.cygwin.com/ml/ecos-discuss/2003-07/msg00036.html for a
>> concise
>> explanation). I don't have any destructor dependencies so I simply
>> supplied my own definitions for these symbols:
>>
>>
>>
>> #if CLICK_LINUXMODULE
>>
>> void* __cxa_atexit = &__cxa_atexit;
>>
>> void* __dso_handle = &__dso_handle;
>>
>> #endif
>>
>>
>>
>> Gcc inserts the undefined symbols __cxa_guard_acquire and
>> __cxa_guard_release into the code to prevent the problem of c++ scoped
>> static initialization not being thread safe
>> (http://blogs.msdn.com/oldnewthing/archive/2004/03/08/85901.aspx). One
>> solution to this is to not use static variables at block scope.
>> Unfortunately this isn't an option for me since I've run into the
>> "static
>> initialization order fiasco". Appending "-fno-threadsafe-statics" to the
>> end of LINUXCFLAGS in the linuxmodule Makefile suppresses the symbols,
>> but
>> leaves me open to the thread safe issue.
>>
>>
>>
>> Does anyone have a solution for the __cxa_guard_acquire/release problem?
>> Or any ideas as to how to proceed?
>>
>>
>>
>> Thank You,
>>
>> Kevin Springborn
>>
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>