Re: GC and Coroutines

I found this old discussion: http://www.hpl.hp.com/hosted/linux/mail-archives/gc/2007-August/001823.html

And I wonder if that issue was ever solved and how it could be related with mine?

On Jan 28, 2014, at 6:48 PM, Kjetil Matheussen <[email protected]> wrote:

> On Tue, Jan 28, 2014 at 10:35 PM, Juan Wajnerman
> <[email protected]> wrote:
>> I made the stack and the coroutine variables (might be the same value, right?) as global but it still crashes.
>> Something I noticed is that when I call co_create() without a stack (it allocates its own stack) it works fine if I didn't call GC_malloc() before.
>> In other words, it crashes if I call GC_malloc() in the main function.
> 
> To be honest, I didn't use BDW-GC with libpcl, but a different
> conservative garbage collector.
> It should have worked with the garbage collector I used.
> 
> Why BDW-GC fails here, I don't know, but the stack trace below might
> give someone
> with more knowledge about BDW-GC an idea:
> 
> 
> (gdb) bt
> #0  0x0000000000419b00 in GC_push_all_eager ()
> #1  0x0000000000419b5c in GC_push_all_stack ()
> #2  0x000000000040570c in GC_push_all_stack_sections ()
> #3  0x000000000040c323 in GC_push_all_stacks ()
> #4  0x0000000000408561 in GC_default_push_other_roots ()
> #5  0x00000000004058bc in GC_push_roots ()
> #6  0x0000000000417ed8 in GC_mark_some ()
> #7  0x000000000040ea9f in GC_stopped_mark ()
> #8  0x000000000040e71a in GC_try_to_collect_inner ()
> #9  0x000000000040fae3 in GC_collect_or_expand ()
> #10 0x000000000040fdfb in GC_allocobj ()
> #11 0x0000000000415d4e in GC_generic_malloc_inner ()
> #12 0x0000000000415efa in GC_generic_malloc ()
> #13 0x0000000000416334 in GC_core_malloc ()
> #14 0x000000000040a2a4 in GC_malloc ()
> #15 0x0000000000404a63 in real_coroutine_body (sbase=0x6bff90,
> realarg=0x6b8000) at test2.c:12
> #16 0x000000000040708c in GC_call_with_stack_base ()
> #17 0x0000000000404a97 in coroutine_stub (arg=0x0) at test2.c:21
> #18 0x000000000041ada5 in co_runner ()
> #19 0x0000003b49446370 in ?? () from /lib64/libc.so.6
> #20 0x0000000000000000 in ?? ()
> (gdb)
> 
> 
>> 
>> On Jan 28, 2014, at 6:16 PM, Kjetil Matheussen <[email protected]> wrote:
>> 
>>> On Tue, Jan 28, 2014 at 9:36 PM, Juan Wajnerman <[email protected]> wrote:
>>>> I'm not sure if I understand how I'm supposed to use the GC_stack_base info.
>>>> I tried to call GC_add_root using the mem_base but with no luck so far.
>>>> 
>>>> Here is a small example of what I'm trying to run:
>>>> https://gist.github.com/waj/8675658
>>>> In my machine it crashes after 60 or 70 iterations.
>>>> 
>>>> The stack space allocated for the coroutine is also allocated with the GC so
>>>> it shouldn't be necessary to register that area, right?
>>> 
>>> Yes, but I think the problem with your example is
>>> that  the pointer to the stack variable in main is not
>>> tracable inside the coroutine. To test that theory,
>>> it should work if you just make it into a global variable.
>>> 
>>> If you run more coroutines, you also need to add
>>> the context of them to the GC roots.
>>> 
>>> For my program, it was enough just doing this:
>>> 
>>> coroutine_t c
>>> GC_add_root(c, c+ MAX(sizeof(ucontext_t), sizeof(jmp_buf)))
>> 
>> 
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