[Openmcl-devel] 1.8 prerelease

Antony lisp.linux at gmail.com
Tue Apr 10 16:09:58 UTC 2012


I applied the patch below against the 1.8 (after svn update) on freebsd 
9.0 .
My application test code now runs good, so does hitting hunchentoot with 
wget :)

Thank you
-Antony

On 3/15/2012 11:00 AM, Gary Byers wrote:
> That (using a script that runs wget instead of using ab) didn't seem
> to make a difference, but changing the vm so that it had 2 CPUs instead
> of 1 caused it to crash reliably.
>
> I looked at a couple of core dumps but didn't fully understand what I 
> saw.
> In both cases, the SIGSEGV occurred around the point where a thread is
> about to enter a handler for the signal used by the GC to suspend other
> threads.  For obscure reasons, a lot of CCL's signal handlers are run
> on an alternate signal stack, and it occurred to me that the particular
> case of the "suspend" signal's handler likely didn't need to be (and at
> the very least this problem would be easier to debug if it wasn't.  I
> changed how that signal was handled, and haven't been able to reproduce
> the problem since.
>
> It doesn't make much sense (yet) that this would fix the problem (and all
> that I know is that I didn't see the problem after making the 
> change.)  If
> there's a general problem with the alternate signal stack mechanism or
> CCL's use of it, that problem would still be there (other signal handlers
> more clearly need to use that mechanism.)
>
> In any case, there does seem to be a problem there (somewhere) and it 
> seems
> likely that the problem you've seen is the same one that I saw.  The 
> small
> change below seemed to at least avoid the problem in your test case, but
> I don't claim that it really fixes it or that I even understand the 
> problem
> at this point ...
>
> [ccl/lisp-kernel] gb at loser> svn diff x86-exceptions.c
> Index: x86-exceptions.c
> ===================================================================
> --- x86-exceptions.c    (revision 15251)
> +++ x86-exceptions.c    (working copy)
> @@ -2292,10 +2292,8 @@
>  #endif
>
>  #ifdef USE_SIGALTSTACK
> -#define SUSPEND_RESUME_HANDLER altstack_suspend_resume_handler
>  #define THREAD_KILL_HANDLER altstack_thread_kill_handler
>  #else
> -#define SUSPEND_RESUME_HANDLER arbstack_suspend_resume_handler
>  #define THREAD_KILL_HANDLER arbstack_thread_kill_handler
>  #endif
>
> @@ -2311,8 +2309,8 @@
>    thread_suspend_signal = SIG_SUSPEND_THREAD;
>    thread_kill_signal = SIG_KILL_THREAD;
>
> -  install_signal_handler(thread_suspend_signal, (void 
> *)SUSPEND_RESUME_HANDLER,
> -             RESERVE_FOR_LISP|ON_ALTSTACK|RESTART_SYSCALLS);
> +  install_signal_handler(thread_suspend_signal, (void 
> *)suspend_resume_handler,
> +             RESERVE_FOR_LISP|RESTART_SYSCALLS);
>    install_signal_handler(thread_kill_signal, (void 
> *)THREAD_KILL_HANDLER,
>               RESERVE_FOR_LISP|ON_ALTSTACK);
>  }
>
>
> On Thu, 15 Mar 2012, Antony wrote:
>
>> On 3/14/2012 10:55 AM, Gary Byers wrote:
>>> I just tried this with the current trunk CCL on FreeBSD 9.0 running on
>>> a VMWare VM on a Mac. "ab -n 2000 -c 4 https://localhost:8083/" ran to
>>> completion (though every request got "SSL read failed - closing
>>> connection", presumably because ab can't deal with self-signed 
>>> certificates.)
>>>
>>> Last month, I don't think that I was sure whether there was a problem
>>> with CCL and FreeBSD 9.0 or whether there was a problem with FreeBSD
>>> 9.0 and the virtualization software that you were using.  The fact
>>> that this worked for me (as well as it did) makes me more suspicious
>>> of the latter at this point.
>>>
>>> CCL is very sensitive to the format of a signal context (a data 
>>> structure
>>> that describes the machine state at the time that an exception 
>>> occurred.)
>>> At some point, the size and layout of the machine-dependent parts of a
>>> signal context will change in some way (to accommodate AVX and 256-bit
>>> vector registers.)  I don't think that FreeBSD has made any such change
>>> as of 9.0, and FreeBSD has generally been very good (at least since 
>>> 5.x)
>>> about maintaining backward compatibility at this level.
>>>
>> I converted the bsd vm to play in VMWare vmplayer.
>> Ran the same test. CCL segfaulted after about 80 requests.
>> Could you try with the script I mentioned at
>> http://clozure.com/pipermail/openmcl-devel/2012-February/013376.html
>> since it completes the requests even with self signed certs unlike  ab
>> I guess it doesn't make much difference, but its a relatively easy 
>> thing to try
>>
>> -Antony
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>> Openmcl-devel at clozure.com
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>>
>>




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