[Gc] GC_INIT? Threads?
Bruce Hoult
bruce at hoult.org
Mon Aug 19 22:00:59 PDT 2013
Once again, it's not crashing, it's a controlled exit because it detected
something wrong.
Try using these (from gc.h)
call GC_allow_register_threads() from your main program, after GC_INIT()
call GC_register_my_thread() at the start of the main function for each
thread you create. (and GC_unregister_my_thread() at the end)
You may also find GC_call_with_stack_base() useful.
/* Explicitly enable GC_register_my_thread() invocation. */
/* Done implicitly if a GC thread-creation function is called (or */
/* implicit thread registration is activated). Otherwise, it must */
/* be called from the main (or any previously registered) thread */
/* between the collector initialization and the first explicit */
/* registering of a thread (it should be called as late as possible). */
GC_API void GC_CALL GC_allow_register_threads(void);
/* Register the current thread, with the indicated stack base, as */
/* a new thread whose stack(s) should be traced by the GC. If it */
/* is not implicitly called by the GC, this must be called before a */
/* thread can allocate garbage collected memory, or assign pointers */
/* to the garbage collected heap. Once registered, a thread will be */
/* stopped during garbage collections. */
/* This call must be previously enabled (see above). */
/* This should never be called from the main thread, where it is */
/* always done implicitly. This is normally done implicitly if GC_ */
/* functions are called to create the thread, e.g. by including gc.h */
/* (which redefines some system functions) before calling the system */
/* thread creation function. Nonetheless, thread cleanup routines */
/* (eg., pthread key destructor) typically require manual thread */
/* registering (and unregistering) if pointers to GC-allocated */
/* objects are manipulated inside. */
/* It is also always done implicitly on some platforms if */
/* GC_use_threads_discovery() is called at start-up. Except for the */
/* latter case, the explicit call is normally required for threads */
/* created by third-party libraries. */
/* A manually registered thread requires manual unregistering. */
GC_API int GC_CALL GC_register_my_thread(const struct GC_stack_base *);
/* Unregister the current thread. Only an explicitly registered */
/* thread (i.e. for which GC_register_my_thread() returns GC_SUCCESS) */
/* is allowed (and required) to call this function. (As a special */
/* exception, it is also allowed to once unregister the main thread.) */
/* The thread may no longer allocate garbage collected memory or */
/* manipulate pointers to the garbage collected heap after making */
/* this call. Specifically, if it wants to return or otherwise */
/* communicate a pointer to the garbage-collected heap to another */
/* thread, it must do this before calling GC_unregister_my_thread, */
/* most probably by saving it in a global data structure. Must not */
/* be called inside a GC callback function (except for */
/* GC_call_with_stack_base() one). */
GC_API int GC_CALL GC_unregister_my_thread(void);
On Tue, Aug 20, 2013 at 4:48 PM, The Devils Jester <
thedevilsjester at gmail.com> wrote:
> The only output I get, aside from the stack trace is:
> Collecting from unknown thread
> Abort trap: 6
>
> My application is organized as follows:
>
> MAIN APP (does not use GC)
> GC_INIT()
> NEW THREAD
> CALL LIBRARY FUNCTION (library uses GC)
>
> This crashes, while
>
> MAIN APP (does not use GC)
> GC_INIT()
> CALL LIBRARY FUNCTION (library uses GC)
>
> Works perfectly fine.
>
> What am I doing wrong? Do I have to initialize the GC in some special
> fashion?
>
>
> On Mon, Aug 19, 2013 at 11:35 PM, Bruce Hoult <bruce at hoult.org> wrote:
>
>> That's not a crash, it's a deliberate abort because some sanity-checking
>> code found that your world was insane. There are several things that can go
>> wrong inside GC_push_all_stacks, so it would be helpful to have the
>> message that GC_abort() printed.
>>
>> However, you should always call GC_INIT() from your main program, and as
>> early as possible.
>>
>> On some versions and platforms GC_INIT() installs code that registers
>> threads in a GC data structure because it's not possible to ask the OS for
>> all your threads. If you call GC_INIT() from a new thread on those
>> platforms then that thread will remain unregistered, which is one of the
>> things that will make GC_push_all_stacks abort later.
>>
>>
>>
>> On Tue, Aug 20, 2013 at 4:10 PM, The Devils Jester <
>> thedevilsjester at gmail.com> wrote:
>>
>>> I have a library that makes heavy use of of the GC, and it works quite
>>> well when everything (the app, and the library) is in one thread. I call
>>> GC_INIT in the app, and all is well.
>>>
>>> If, however, the app creates a new thread that calls the library
>>> function, then it crashes when the GC does its magic (below I have pasted
>>> some relevant output).
>>>
>>> Is there some trick to using GC on a separate thread? Do I call GC_INIT
>>> from the main thread, or the one that calls the library functions?
>>>
>>>
>>> 0 libsystem_kernel.dylib 0x00007fff8ad14212 __pthread_kill +
>>> 10
>>> 1 libsystem_c.dylib 0x00007fff90d01b54 pthread_kill + 90
>>> 2 libsystem_c.dylib 0x00007fff90d45dce abort + 143
>>> 3 libgc.1.dylib 0x000000010357676e GC_abort + 97
>>> 4 libgc.1.dylib 0x000000010357b413 GC_push_all_stacks
>>> + 285
>>> 5 libgc.1.dylib 0x000000010357396e GC_mark_some + 377
>>> 6 libgc.1.dylib 0x000000010356d73e GC_stopped_mark +
>>> 148
>>> 7 libgc.1.dylib 0x000000010356d645
>>> GC_try_to_collect_inner + 245
>>> 8 libgc.1.dylib 0x000000010356e302
>>> GC_collect_or_expand + 147
>>> 9 libgc.1.dylib 0x000000010356e51a GC_allocobj + 228
>>> 10 libgc.1.dylib 0x0000000103572515
>>> GC_generic_malloc_inner + 249
>>> 11 libgc.1.dylib 0x00000001035725dd GC_generic_malloc
>>> + 79
>>> 12 libgc.1.dylib 0x00000001035728c0 GC_core_malloc +
>>> 196
>>>
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>>
>>
>
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