Date: Fri, 31 Dec 2010 13:35:14 +0100 From: John Marino <freebsdml@marino.st> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-threads@freebsd.org Subject: Re: AMD64 version of GNAT Ada compiler broken due to libthr Message-ID: <4D1DCE02.3050601@marino.st> In-Reply-To: <20101231122225.GK90883@deviant.kiev.zoral.com.ua> References: <4D1DC299.2090808@marino.st> <20101231122225.GK90883@deviant.kiev.zoral.com.ua>
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Hi Kostik,
You're right, that was an oversight. I'm using release 8.1, but I tried
troubleshooting this months ago on 8.0 and the result was identical.
I'm well above my head here. I don't know what I should be looking for.
Here's the dissembled _umtx_op_err function, along with the
backtraces of the other two threads. They didn't look that interesting
to me the first time.
-- john
Starting program: /usr/home/marino/test_gnat/test_c9a009c/c9a009c
[New LWP 100086]
[New Thread 800a041c0 (LWP 100086)]
[New Thread 800a0ae40 (LWP 100051)]
[New Thread 800a64c80 (LWP 100073)]
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 800a64c80 (LWP 100073)]
0x00007fffffbfeb19 in ?? ()
Cannot set lwp 100073 registers: Invalid argument
An error occurred while in a function called from GDB.
Evaluation of the expression containing the function
(_umtx_op_err) will be abandoned.
When the function is done executing, GDB will silently stop.
Dump of assembler code for function _umtx_op_err:
0x00000008006923c0 <+0>: mov $0x1c6,%rax
0x00000008006923c7 <+7>: mov %rcx,%r10
0x00000008006923ca <+10>: syscall
0x00000008006923cc <+12>: retq
0x00000008006923cd <+13>: nop
0x00000008006923ce <+14>: nop
0x00000008006923cf <+15>: nop
0x00000008006923d0 <+16>: mov 0x102d09(%rip),%rax #
0x8007950e0
0x00000008006923d7 <+23>: push %rbx
0x00000008006923d8 <+24>: cmp $0xffffffffffffffff,%rax
0x00000008006923dc <+28>: je 0x8006923f5 <_umtx_op_err+53>
0x00000008006923de <+30>: lea 0x102cfb(%rip),%rbx #
0x8007950e0
0x00000008006923e5 <+37>: callq *%rax
0x00000008006923e7 <+39>: mov -0x8(%rbx),%rax
0x00000008006923eb <+43>: sub $0x8,%rbx
0x00000008006923ef <+47>: cmp $0xffffffffffffffff,%rax
0x00000008006923f3 <+51>: jne 0x8006923e5 <_umtx_op_err+37>
0x00000008006923f5 <+53>: pop %rbx
0x00000008006923f6 <+54>: retq
0x00000008006923f7 <+55>: nop
End of assembler dump.
[Switching to thread 2 (Thread 800a041c0 (LWP 100086))]#0
0x00000008006923cc in _umtx_op_err () at
/usr/src/lib/libthr/arch/amd64/amd64/_umtx_op_err.S:37
37 RSYSCALL_ERR(_umtx_op)
#0 0x00000008006923cc in _umtx_op_err ()
at /usr/src/lib/libthr/arch/amd64/amd64/_umtx_op_err.S:37
#1 0x00000008006904c5 in cond_wait_common (cond=<value optimized out>,
mutex=0x800a0bb50, abstime=0x0, cancel=1)
at /usr/src/lib/libthr/thread/thr_cond.c:204
#2 0x000000000040bfeb in
system.tasking.stages.vulnerable_complete_master ()
at s-tassta.adb:1696
#3 0x000000000040620a in c9a009c () at c9a009c.adb:44
[Switching to thread 4 (Thread 800a64c80 (LWP 100073))]#0
0x00007fffffbfeb19 in ?? ()
#0 0x00007fffffbfeb19 in ?? ()
#1 0x000000000040d655 in system.tasking.stages.task_wrapper (
self_id=0x800a52500) at s-tassta.adb:1207
#2 0x0000000800688621 in thread_start (curthread=0x800a64c80)
at /usr/src/lib/libthr/thread/thr_create.c:288
#3 0x0000000000000000 in ?? ()
Kostik Belousov wrote:
> On Fri, Dec 31, 2010 at 12:46:33PM +0100, John Marino wrote:
>> For several months I have been getting the GNAT Ada compiler to work
>> properly on the four major BSDs. The i386 FreeBSD, the i386 Dragonfly
>> BSD, and the x86_64 Dragonfly BSD ports are currently perfect. The i386
>> and x86_64 ports of NetBSD are nearly perfect, and only lack a
>> functional DWARF2 unwind mechanism, and the OpenBSD ports are in pretty
>> good shape too. The progress for this work can be seen at
>> http://www.dragonlace.net
>>
>> However the AMD64 FreeBSD version is unusable and it's due to libthr.
>> I'm not sure why the i386 version works with libthr and AMD64 version
>> doesn't. For all four BSDs, there is no configuration difference for
>> threading between architectures.
>>
>> The problem seems to be with the pthread_cond_wait functionality.
>>
>> I've logged a test case segfault via gdb7.1 below. I would greatly
>> appreciate some help in determining where the problem lies. If this
>> problem can be solved, it will likely result in a perfect port of the
>> GNAT Ada compiler for FreeBSD AMD64, something that has not existed before.
>>
> First, you did not specified which version of the base system you use.
>
> Second, I suspect that the backtrace you have shown is not from the
> thread that generated SIGSEGV. Switch to other threads and see their
> backtraces, I am almost sure that there will be something more interesting.
>
> Just to be sure, in gdb, disassemble _umtx_op_err() and see which
> instruction is executed when SIGSEGV generated. I think that the thread
> with the backtrace below is sleeping in syscall.
>
>> Regards,
>> John
>>
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