Re[10]: [Gc]: boehm port to Native Client

Ivan Maidanski ivmai at mail.ru
Sun Sep 15 07:56:42 PDT 2013


Hi Elijah,

I found several commits from you to mono repository this year (8 months ago) including ARM support:
*  https://github.com/ivmai/bdwgc/commit/204bcc6ede64402ca3ff2b165fc47a63374c68b1
*  https://github.com/ivmai/bdwgc/commit/b328e8824e6ffa7cbd38c83e26433bee24bd3bb1
*  https://github.com/ivmai/bdwgc/commit/21f0df75f5bac02619fb6fa4bcf5b49b169aeb1a

Anything to upstream?
Thank you.


Tue,  6 Mar 2012, 7:51 -08:00 from Elijah Taylor <elijahtaylor at google.com>:
>That's correct that mono master doesn't have these changes. I'm working to get these changes in upstream mono so I can retire my fork.
>I'll let you know of further changes in the future but I would call it pretty stable at this point and don't expect it to change for some time.
>On Mar 6, 2012 12:11 AM, "Ivan Maidanski" < ivmai at mail.ru > wrote:
>>Hi Elijah,
>>
>>Thank you for your reply.
>>In future, please also CC to this ML on committing to mono/libgc.
>>Unfortunately, i don't have time to check it on NaCl target.
>>
>>PS. I don't see anything else in mono master relevant to GC and NaCl in 2011.
>>(for convenience, we have a branch "mono_libgc" which is a copy of mono/master -  https://github.com/ivmai/bdwgc/tree/mono_libgc )
>>
>>05 03 2012, 23:11 Elijah Taylor < elijahtaylor at google.com >:
>>> Hi Ivan,
>>>
>>> nacl_register_gc_hooks is defined in libnacl.a.  Unfortunately, that
>>> library is really only meaningful with our newlib toolchain.  Thanks for
>>> reminding me, I've filed a bug:
>>>  https://code.google.com/p/nativeclient/issues/detail?id=2635
>>>
>>> You may want to consider taking a couple more changes to that file (and
>>> other parts of libgc that we changed) in order to get something that will
>>> build and run with our glibc toolchain.  From September through January, a
>>> lot of changes went into Mono to make things work cleanly with our glibc,
>>> and a decent amount was getting libgc working in the different environment.
>>>  In fact, I've pretty much dropped support for using this with our newlib
>>> version.
>>>
>>> -Elijah
>>>
>>> On Mon, Mar 5, 2012 at 7:01 AM, Ivan Maidanski < ivmai at mail.ru > wrote:
>>>
>>> > Hi Elijah,
>>> >
>>> > I've cherry-picked your latest commit regarding NaCl from mono/libgc to
>>> > BDWGC master branch (with minor modifications):
>>> >
>>> >  https://github.com/ivmai/bdwgc/commit/14f2760d584c18fc8a1f305f5ed0a6d13ff5918a
>>> >
>>> > I wonder where is nacl_register_gc_hooks defined?
>>> >
>>> > Thanks.
>>> >
>>> > 18 04 2011, 22:31 Elijah Taylor < elijahtaylor at google.com >:
>>> > > Hi Ivan,
>>> > >
>>> > > If I can add a couple of functions to our pthread implementation
>>> > > (pthread_getattr_np and pthread_getattr_getstack) then we should be able
>>> > to
>>> > > just use the GC_LINUX_THREADS version and take off the "!defined(NACL)".
>>> > >  I'll let you know of my progress when I have something to report.
>>> > >
>>> > > -Elijah
>>> > >
>>> > > On Sat, Apr 16, 2011 at 1:48 AM, Ivan Maidanski < ivmai at mail.ru > wrote:
>>> > >
>>> > > > Hi Elijah,
>>> > > >
>>> > > > Could you also provide GC_get_stack_base() implementation for NaCl?
>>> > (just
>>> > > > for the completeness of the port)
>>> > > >
>>> > > > Thanks.
>>> > > >
>>> > > > Sat, 22 Jan 2011 16:23:32 -0800 Elijah Taylor < elijahtaylor at google.com
>>> > >:
>>> > > >
>>> > > > Hi Ivan,
>>> > > >
>>> > > > Sorry I haven't gotten back to you yet, I've been busy with other
>>> > things
>>> > > > this last week.  I'm planning on addressing the feedback you've given
>>> > me so
>>> > > > far in the next week, and I can send you a more detailed response to
>>> > your
>>> > > > other questions at that time.  Thanks for the help so far.
>>> > > >
>>> > > > -Elijah
>>> > > >
>>> > > >
>>> > > > On Sat, Jan 22, 2011 at 9:09 AM, Ivan Maidanski < ivmai at mail.ru <
>>> >  https://sentmsg?compose&To=ivmai@mail.ru >
>>> > > > > wrote:
>>> > > >
>>> > > >> Hi Elijah,
>>> > > >>
>>> > > >> Any progress or comments?
>>> > > >>
>>> > > >> Sat, 15 Jan 2011 15:36:47 +0300 Ivan Maidanski < ivmai at mail.ru <
>>> >  https://sentmsg?compose&To=ivmai@mail.ru >
>>> > > >> >:
>>> > > >>
>>> > > >> > Hello Elijah,
>>> > > >> >
>>> > > >> > Fri, 14 Jan 2011 15:36:34 -0800 письмо от Elijah Taylor <
>>> > > >> >  elijahtaylor at google.com <
>>> >  https://sentmsg?compose&To=elijahtaylor@google.com >(sentmsg?compose&To=
>>> > > >>  elijahtaylor at google.com <
>>> >  https://sentmsg?compose&To=elijahtaylor@google.com >)
>>> > > >> >:
>>> > > >> >
>>> > > >> > > Hi Ivan,
>>> > > >> > >
>>> > > >> > > Thanks for taking a look, I'm pleasantly surprised by the level of
>>> > > >> detail
>>> > > >> > > here.  Specific replies inline:
>>> > > >> > >
>>> > > >> > >
>>> > > >> > > On Fri, Jan 14, 2011 at 2:50 PM, Ivan Maidanski <  ivmai at mail.ru <
>>> >  https://sentmsg?compose&To=ivmai@mail.ru >
>>> > > >> > (sentmsg?compose&To= ivmai at mail.ru <
>>> >  https://sentmsg?compose&To=ivmai@mail.ru >)
>>> > > >> > wrote:
>>> > > >> > >
>>> > > >> > > - the patch in  naclports repository contains a typo in a macro
>>> > > >> definition
>>> > > >> > > > (MAC_TYPE -> MACH_TYPE);
>>> > > >> > >
>>> > > >> > > Oops, will fix.
>>> > > >> >
>>> > > >> > Why not to leave MACH_TYPE as-is (e.g. "I386", etc.)? NaCl is a
>>> > kind of
>>> > > >> OS not
>>> > > >> > a kind of machine hardware.
>>> > > >> > Is eg. I386 defined for x86?
>>> > > >> >
>>> > > >> > Also, please add a mapping comment in gcconfig.h (around "Feel free
>>> > to
>>> > > >> add
>>> > > >> > more clauses here").
>>> > > >> >
>>> > > >> > >
>>> > > >> > > > - the patch in  naclports repository looks more suitable for gc
>>> > v72
>>> > > >> than
>>> > > >> > > > that for mono/libgc;
>>> > > >> > > >
>>> > > >> > >
>>> > > >> > > This patch is meant to be applied to vanilla gc6.8.  The
>>> > mono/libgc
>>> > > >> port is
>>> > > >> > > already patched directly into mono's code repository.
>>> > > >> >
>>> > > >> > Yes, I only meant the vanilla gc6.8 patch contains some more code
>>> > (eg,
>>> > > >> for
>>> > > >> > PARALLEL_MARK) not present in mono/libgc.
>>> > > >> >
>>> > > >> > > > - gc_pthread_redirects.h (which is a public one) should not test
>>> > > >> NACL
>>> > > >> > macro
>>> > > >> > > > (or, at least, while less desirable, it should be prefixed with
>>> > > >> GC_);
>>> > > >> > > >
>>> > > >> > >
>>> > > >> > > Ok, makes sense, I think I didn't realize this was a public
>>> > header.
>>> > > >>  Though
>>> > > >> > > that explains why I had to add a test for __native_client__
>>> >  (which is
>>> > > >> > > defined in our toolchain).  I'll fix this.
>>> > > >> > >
>>> > > >> > > > - it's not clear why you need to explicitly undef STACK_GRAN,
>>> > > >> > USE_M[UN]MAP,
>>> > > >> > > > etc. in gcconfig.h;
>>> > > >> > > >
>>> > > >> > >
>>> > > >> > > I'll do some investigation, but IIRC these were needed at one
>>> > point
>>> > > >> for me.
>>> > > >> > > There's a good chance these may be unnecessary and vestigial.
>>> > > >> >
>>> > > >> > There should none "undef" (no other target undefining them).
>>> > > >> >
>>> > > >> > If mmap is supported by NaCl then it might be possible to support
>>> > > >> > USE_M[UN]MAP.
>>> > > >> >
>>> > > >> > > > - is MPROTECT_VDB supported or not?;
>>> > > >> > >
>>> > > >> > > Is MPROTECT_VDB equivalent to catching protection violations in
>>> > the GC
>>> > > >> code?
>>> > > >> > > If so, then no, we don't support anything like that right now.
>>> > > >>  Protection
>>> > > >> > > violation in NaCl == instant death.
>>> > > >> >
>>> > > >> > Ok, so MPROTECT_VDB (i.e., incremental/generation collection) is not
>>> > > >> > supported.
>>> > > >> >
>>> > > >> > > > - if you you want to port gc72 please use the recent CVS
>>> > snapshot
>>> > > >> (it
>>> > > >> > would
>>> > > >> > > > be easier to me to review and commit it);
>>> > > >> > >
>>> > > >> > > I've been grabbing source from
>>> > > >> > >   https://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/
>>> > > >> > ( https://www.hpl.hp.com/personal/Hans_Boehm/gc/gc_source/ )  ... can
>>> > you
>>> > > >> point
>>> > > >> > me
>>> > > >> > > to where I should be getting the latest?  It's not immediately
>>> > obvious
>>> > > >> to
>>> > > >> > > me.
>>> > > >> >
>>> > > >> >  https://bdwgc.cvs.sourceforge.net/viewvc/bdwgc/bdwgc/
>>> > > >> > (For convenience, I have a recent snapshot as a tarball which I use
>>> > for
>>> > > >> my
>>> > > >> > project -
>>> > > >> >
>>> >  https://www.ivmaisoft.com/_mirror/hpl/bdwgc-7_2alpha5-20110107.tar.bz2 )
>>> > > >> >
>>> > > >> > > - not sure that HEURISTIC1 really works reliably there (in short,
>>> > > >> HEURISTIC1
>>> > > >> > > > means you treat stack pointer at GC_init call as stack bottom -
>>> > is
>>> > > >> it
>>> > > >> > > > guaranteed that GC_init call is always done at higher stack
>>> > > >> addresses than
>>> > > >> > > > any other GC call);
>>> > > >> > > >
>>> > > >> > >
>>> > > >> > > HEURISTIC2 will definitely not work for us as it wants to use a
>>> > > >> segfault to
>>> > > >> > > detect running over the stack.  I've set STACK_GRAN to 64K, so as
>>> > long
>>> > > >> as
>>> > > >> > > the stack doesn't grow beyond that size before GC_init, we should
>>> > be
>>> > > >> ok,as
>>> > > >> > > right?  The stack for the main thread right now in NaCl lives at a
>>> > > >> fixed
>>> > > >> > > address usually, but that isn't guaranteed for all future time,
>>> > so I'd
>>> > > >> > > prefer not to hard code magic numbers here.
>>> > > >> >
>>> > > >> > No, HEURISTIC2 won't work without signals, but there are other
>>> > > >> alternatives:
>>> > > >> > - if threads-support is on then is it possible to use
>>> > > >> > USE_GET_STACKBASE_FOR_MAIN?;
>>> > > >> > - is it possible to LINUX_STACKBOTTOM (if we are on real Linux)?
>>> > > >> > - for NaCl on Cygwin, it might be possible to use
>>> > > >> GC_get_[main_]stack_base
>>> > > >> > based on __asm__ ("%fs:4").
>>> > > >> >
>>> > > >> > > > - is the GC port compilable (and working) on other (non-Linux)
>>> > > >> platforms
>>> > > >> > > > (eg., Cygwin);
>>> > > >> > > >
>>> > > >> > >
>>> > > >> > > Native Client is meant to be portable, so it should run on any
>>> > x86 or
>>> > > >> x86-64
>>> > > >> > > machine once it's built.  In terms of building, I haven't built
>>> > this
>>> > > >> gc port
>>> > > >> > > personally on Mac or Windows, but I just checked our build bot
>>> > logs
>>> > > >> and they
>>> > > >> > > seem to be building ok on Mac and in Cygwin.
>>> > > >> >
>>> > > >> > So, eg. DARWIN, GC_DARWIN_THREADS,  WIN32, CYGWIN, GC_WIN32_THREADS
>>> > > >> won't ever
>>> > > >> > be defined when building NaCl, right?
>>> > > >> > Is GC_LINUX_THREADS defined when building NaCl with multi-threaded
>>> > > >> support?
>>> > > >> >
>>> > > >> > I have very little knowledge of NaCl - could you briefly explain
>>> > what
>>> > > >> does
>>> > > >> > stand for NaCl portability - is it possible to call Win32 API if I'm
>>> > > >> compiling
>>> > > >> > on Cygwin or should I use the NaCl API (and, thus, the compiled
>>> > binary
>>> > > >> code
>>> > > >> > will run on any x86 target)?
>>> > > >> >
>>> > > >> > If NaCl is some kind of OS then LINUX, DARWIN, WIN32, etc shouldn't
>>> > be
>>> > > >> defined
>>> > > >> > (even if __linux__ defined) if NACL.
>>> > > >> > Same for GC_xxx_THREADS - I think GC_NACL_THREADS could be defined
>>> > > >> instead of
>>> > > >> > GC_LINUX_THREADS, etc.
>>> > > >> >
>>> > > >> > I also think that I386 and X86_64 should stay defined for
>>> > respectively
>>> > > >> the
>>> > > >> > corresponding CPU type (I guess it is already for NaCl but i haven't
>>> > > >> checked
>>> > > >> > yet)
>>> > > >> > I think there should be 2 ifdef NACL define OS_TYPE "NACL" ...
>>> > sections
>>> > > >> (one
>>> > > >> > for every supported CPU).
>>> > > >> >
>>> > > >> > > > - for non-static GC-internal symbols use GC_ prefix (eg. for
>>> > > >> > > > nacl_thread_parked);
>>> > > >> > > > - define SIG_SUSPEND to -1 (instead of 0) as it is returned by
>>> > > >> > > > GC_get_suspend_signal;
>>> > > >> > > > - GC functions called from NaCl it self (eg,
>>> > nacl_pre_syscall_hook)
>>> > > >> shoud
>>> > > >> > > > be tagged with some attribute (like public GC functions are)
>>> > both
>>> > > >> for code
>>> > > >> > > > readability and to prevent that symbols stripping when compiled
>>> > as a
>>> > > >> > shared
>>> > > >> > > > lib with -DGC_DLL);
>>> > > >> > > >
>>> > > >> > >
>>> > > >> > > I'll address these issues.  (note that NaCl currently doesn't
>>> > support
>>> > > >> shared
>>> > > >> > > libs yet so your dll example won't happen, but I agree that these
>>> > > >> should be
>>> > > >> > > treated like other public GC functions)
>>> > > >> >
>>> > > >> > Ok. But what is eg. nacl_pre_syscall_hook() - a callback from the
>>> > NaCl
>>> > > >> > subsystem? (I guess this should be treated as GC public API)
>>> > > >> >
>>> > > >> > Of course, use STATIC or static where possible (all STATIC symbols
>>> > start
>>> > > >> with
>>> > > >> > GC_, while static typically not).
>>> > > >> > More tips: use GC_INNER and GC_EXTERN for internal global
>>> > variables; use
>>> > > >> > GC_INNER for internal functions.
>>> > > >> >
>>> > > >> > > > - libatomic_ops does not use signals API (except for CAS
>>> > emulation
>>> > > >> which
>>> > > >> > is
>>> > > >> > > > not used for x86/x64).
>>> > > >> > >
>>> > > >> > > I think I saw sigprocmask and related functions and assumed the
>>> > worst,
>>> > > >> but I
>>> > > >> > > see now that's windows code.  Looking at the x86 variants it looks
>>> > > >> like a
>>> > > >> > > NaCl port of libatomic_ops is probably not going to be too bad.
>>> >  I'll
>>> > > >> look
>>> > > >> > > into this eventually.
>>> > > >> >
>>> > > >> > Most probably, it work w/o any porting afforts but it would be good
>>> > to
>>> > > >> port
>>> > > >> > atomic_ops.c (similar to what I did for Win32-pthreads targets - see
>>> > > >> > AO_USE_WIN32_PTHREADS, I guess you should add AO_USE_NACL macro
>>> > testing
>>> > > >> in
>>> > > >> > that file (looks easy to add). I think it's worth doing first (and
>>> > > >> submit me a
>>> > > >> > separate patch for libatomics_op when done).
>>> > > >> >
>>> > > >> > What's about GC_HAVE_BUILTIN_BACKTRACE and GC_CAN_SAVE_CALL_STACKS?
>>> > At
>>> > > >> least,
>>> > > >> > gc.h should be consistent with the GC implementation (I mean eg. if
>>> > > >> > GC_HAVE_BUILTIN_BACKTRACE not supported then it shouldn't be
>>> > defined in
>>> > > >> gc.h
>>> > > >> > regardless of __linux__, _MSC_VER, etc. provided
>>> >  __native_client__).
>>> > > >> Same for
>>> > > >> > GC_ADD_CALLER, GC_RETURN_ADDR.
>>> > > >> >
>>> > > >> > Regards.
>>> > > >> >
>>> > > >> > > > PS. Let me not do the benefits analysis (probably someone else
>>> > can
>>> > > >> do
>>> > > >> > > > this).
>>> > > >> > > >
>>> > > >> > > Well, if the gc7.2 port is as easy as it's looking now, I think
>>> > it's
>>> > > >> > > probably worth doing it.  I would still love to hear anyone chime
>>> > in
>>> > > >> on the
>>> > > >> > > benefits of gc7.2 vs 6.8 though
>>> > > >> > >
>>> > > >> > > > Regards.
>>> > > >> > > >
>>> > > >> > > > Thu, 13 Jan 2011 10:21:03 -0800 Elijah Taylor <
>>> > > >>  elijahtaylor at google.com <
>>> >  https://sentmsg?compose&To=elijahtaylor@google.com >
>>> > > >> > (sentmsg?compose&To= elijahtaylor at google.com <
>>> >  https://sentmsg?compose&To=elijahtaylor@google.com >)
>>> > > >> >:
>>> > > >> > > >
>>> > > >> > > > > Hi GC folks,
>>> > > >> > > >
>>> > > >> > > > > I saw a little chatter in the archives related to porting
>>> > libgc to
>>> > > >> > Native
>>> > > >> > > > Client, so I joined this list to share some details. I'm the
>>> > > >> engineer at
>>> > > >> > > > Google who ported of libgc to Native Client for Mono. I've also
>>> > > >> included a
>>> > > >> > > > patch for vanilla gc6.8 in our naclports repository:
>>> > > >> > > >   https://code.google.com/p/naclports/ (
>>> > > >>  https://code.google.com/p/naclports/ )
>>> > > >> > . This version will be available to
>>> > > >> > > > users that want to use libgc as part of their Native Client
>>> > > >> projects.
>>> > > >> > > >
>>> > > >> > > > > Before porting gc6.8 I had attempted to port one of the newer
>>> > > >> versions,
>>> > > >> > > > gc7.2alpha4, but ran into snags. The largest snag right now I
>>> > think
>>> > > >> is
>>> > > >> > that
>>> > > >> > > > gc 7+ includes libatomic_ops which will require some non-trivial
>>> > > >> effort in
>>> > > >> > > > order to work under Native Client. Most notably we don't support
>>> > > >> signals;
>>> > > >> > > > that was the biggest effort in porting libgc in the first place
>>> > for
>>> > > >> NaCl,
>>> > > >> > > > and I assume that will require the most work in porting
>>> > > >> libatomic_ops too.
>>> > > >> > > >
>>> > > >> > > > > Can someone give me the high level details of what kind of
>>> > things
>>> > > >> we
>>> > > >> > > > might be missing if we only support gc6.8 instead of the latest
>>> > > >> version?
>>> > > >> > > > Because of our thread stopping implementation, we may not even
>>> > > >> benefit
>>> > > >> > from
>>> > > >> > > > some of the newer features. I just wanted to get a sense of
>>> > what the
>>> > > >> > > > benefits are of getting a newer version available for users.
>>> > > >> > > >
>>> > > >> > > > > -Elijah
>>> > > >>
>>> > > >>
>>> > > >
>>> > > >
>>> > >
>>> > >
>>> >
>>>
>>> 

-- 
Иван Майданский
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