[LLVMdev] Issue with std::call_once in PPC64 platform

[Chris Bieneman]

Adding Jiangning Liu to the thread.

Jiangning reported a similar issue on the llvm-commits list on Debian aarch64.

In general it sounds like std::call_once may not really be bug free.

Jiangning, can you please provide your gcc/libstdc++ version?

Thanks,
-Chris


> On Nov 4, 2014, at 9:38 AM, Bill Schmidt <wschmidt at linux.vnet.ibm.com> wrote:
> 
> On Tue, 2014-11-04 at 12:17 -0500, Samuel F Antao wrote:
>> Ok, I'll put a patch together to fix this later today. I'll probably
>> do what Reid was suggesting and use what is already in there for
>> Windows.
> 
> Hm, better hold off on that.  Ulrich Weigand has noted that there is
> invalid code generation occurring around a TLS call.  Looks like is is
> probably a PPC back end problem at the moment.
> 
> Thanks,
> Bill
> 
>> 
>> Thanks,
>> Samuel
>> 
>> Bill Schmidt <wschmidt at linux.vnet.ibm.com> wrote on 11/04/2014
>> 12:11:08 PM:
>> 
>>> From: Bill Schmidt <wschmidt at linux.vnet.ibm.com>
>>> To: Samuel F Antao/Watson/IBM at IBMUS
>>> Cc: azanella at linux.vnet.ibm.com, beanz at apple.com, Hal Finkel 
>>> <hfinkel at anl.gov>, LLVM Dev <llvmdev at cs.uiuc.edu>
>>> Date: 11/04/2014 12:11 PM
>>> Subject: Re: Issue with std::call_once in PPC64 platform
>>> 
>>> On Tue, 2014-11-04 at 11:59 -0500, Samuel F Antao wrote:
>>>> Hi Bill,
>>>> 
>>>> You can find the same issue in the buildbot:
>>>> 
>>>> http://lab.llvm.org:8011/builders/clang-ppc64-elf-linux2/builds/
>>> 16444/steps/compile.llvm.stage2/logs/stdio
>>>> 
>>>> It is failing for me both in BE (gcc 4.8.2) and LE(4.9.1). I am
>>>> compiling with clang 3.5, but those are the gcc toolchains I am
>> using.
>>>> 
>>>> What do you think is the best way to fix this?
>>> 
>>> I don't know what the best fix is, but clearly a fix or revert is
>> needed
>>> since the patch is breaking some platforms.
>>> 
>>> Thanks,
>>> Bill
>>> 
>>>> 
>>>> Thanks!
>>>> Samuel 
>>>> 
>>>> Bill Schmidt <wschmidt at linux.vnet.ibm.com> wrote on 11/04/2014
>>>> 11:45:06 AM:
>>>> 
>>>>> From: Bill Schmidt <wschmidt at linux.vnet.ibm.com>
>>>>> To: Samuel F Antao/Watson/IBM at IBMUS
>>>>> Cc: LLVM Dev <llvmdev at cs.uiuc.edu>, beanz at apple.com, Hal Finkel 
>>>>> <hfinkel at anl.gov>, azanella at linux.vnet.ibm.com
>>>>> Date: 11/04/2014 11:45 AM
>>>>> Subject: Re: Issue with std::call_once in PPC64 platform
>>>>> 
>>>>> Hi Samuel,
>>>>> 
>>>>> I haven't encountered this problem.  What gcc/libstdc++ are you
>>>> using?
>>>>> BE or LE?
>>>>> 
>>>>> Copying Adhemerval in case he has heard of any related issues.
>>>>> 
>>>>> Thanks,
>>>>> Bill
>>>>> 
>>>>> On Mon, 2014-11-03 at 20:19 -0500, Samuel F Antao wrote:
>>>>>> Hi all,
>>>>>> 
>>>>>> I observe that r220932 (Removing the static initializer in
>>>>>> ManagedStatic.cpp by using llvm_call_once to initialize the
>>>>>> ManagedStatic mutex.) is causing tablegen to segfault in PPC
>>>> platforms
>>>>>> during static initialization. The crash happens while calling
>>>>>> std::call_once introduced by this patch in the wrapper used
>> in
>>>>>> getManagedStaticMutex. 
>>>>>> 
>>>>>> I understand this call is buggy for some platforms (or
>> probably
>>>> some
>>>>>> oldish libstdc++ versions). Is this a known issue? Should we
>> guard
>>>>>> LLVM_DEFINE_ONCE_FLAG definition with platform specific macros
>> to
>>>>>> avoid the crash, at least for the moment?
>>>>>> 
>>>>>> Thanks!
>>>>>> Samuel
>>>>>> 
>>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>>> 
>>> 
>> 
>> 
> 
>