[Openmp-dev] OMPT on Windows

Mon Jun 8 09:28:17 PDT 2015

Olga,

I don’t work with Windows, so I would appreciate suggestions from those at Intel who do about how to have the OpenMP runtime interact with the tool in a dynamically linked scenario on Windows. Is the text that Tim included below from the OMPT draft specification enough for you to craft a solution for Windows? If not, how should the OpenMP runtime identify that a tool is present and call a function to set up the tool?

We wanted to avoid creating a security flaw by having the OMP runtime read the name of a dynamically linked library for the tool shared library an environment variable and then load that. This strategy would certainly work, though I would expect to hear that this would create security problems.
--
John Mellor-Crummey         Professor
Dept of Computer Science    Rice University
email: johnmc at rice.edu      phone: 713-348-5179

> On Jun 8, 2015, at 11:05 AM, Cramer, Tim <Cramer at itc.rwth-aachen.de> wrote:
> 
> Hi Olga,
>  
> To be honest: I am not really aware of Windows. As far as I know weak symbols are not supported on Windows, so that we need a different strategy. The OMPT specification [1] says
>  
> “Compiler and linker don't support weak symbols. On systems that don't support weak symbols, different implementation strategies are needed for static and dynamic linking. For a static library implementation of an OpenMP runtime library, the library can provide a stub version of ompt_initialize in a separate object file. In this case, the linker will include the OpenMP library's stub implementation of ompt_initialize only if no tool supplied version is already present when the OpenMP runtime library is used to resolve undefined symbols. An OpenMP implementation used as a dynamic library can define ompt_initialize as a global symbol. The version in the OpenMP library would be invoked only if no tool-supplied implementation of ompt_initialize is statically linked in the executable or a tool library that appears before the OpenMP runtime library in the dynamic library search path during execution.”
>  
> I will discuss with Jonas how / if we can fix this. At least we should ensure that compiling is possible on Windows, at least with deactivating OMPT.
>  
> Regards,
>  
> Tim
>  
> [1] http://openmp.org/mp-documents/ompt-tr2.pdf <http://openmp.org/mp-documents/ompt-tr2.pdf>
>  
>  
> From: Malysheva, Olga [mailto:Olga.Malysheva at intel.com <mailto:Olga.Malysheva at intel.com>] 
> Sent: Thursday, June 04, 2015 2:42 PM
> To: Hahnfeld, Jonas
> Cc: John Mellor-Crummey (johnmc at rice.edu <mailto:johnmc at rice.edu>); Cramer, Tim; 'openmp-dev at dcs-maillist2.engr.illinois.edu <mailto:openmp-dev at dcs-maillist2.engr.illinois.edu>'
> Subject: OMPT on Windows 
>  
>  <>Hi Jonas, 
>  
> How do you intend to support OMPT on Windows? 
> The code currently committed to the project can be compiled only on unix-like systems due to the attribute ‘weak’ specified for the initialization function (in ompt-general.c):
>  
> _OMP_EXTERN __attribute__ (( weak ))
> int ompt_initialize(ompt_function_lookup_t ompt_fn_lookup, const char *version,
>                     unsigned int ompt_version)
> {
>     return no_tool_present;
> }
>  
> Thank you.
>  
> Regards,
> Olga
>  
> -----Original Message-----
> From: openmp-dev-bounces at cs.uiuc.edu <mailto:openmp-dev-bounces at cs.uiuc.edu> [mailto:openmp-dev-bounces at cs.uiuc.edu <mailto:openmp-dev-bounces at cs.uiuc.edu>] On Behalf Of Hahnfeld, Jonas
> Sent: Thursday, April 9, 2015 4:25 PM
> To: 'openmp-dev at dcs-maillist2.engr.illinois.edu <mailto:openmp-dev at dcs-maillist2.engr.illinois.edu>'
> Cc: John Mellor-Crummey (johnmc at rice.edu <mailto:johnmc at rice.edu>); Cramer, Tim
> Subject: [Openmp-dev] Patches to support OMPT
>  
> Hi all!
>  
> After some months of work, we would like to share our patches to add support for OMPT[1] to this version of the Intel runtime.
> Implementation was mainly done by John Mellor-Crummey from Rice University in a repository at Google Code[2].
>  
> Support for OMPT is disabled by default and therefore has to be enabled
> explicitly:
> With CMake, define "ompt-support": $ cmake -Dompt-support=true ..
> build.pl works nearly the same: $ make build_args="--ompt-support=on"
> With this switch, ompt-blame and ompt-trace will be enabled as well which can be disabled separately.
>  
> We've uploaded the patches to LLVM's Phabricator. Some short explanation:
> 0001-kmp_lock-Change-return-type-of-release-functions-fro.patch[3]
> This is a preparation patch to get information about the actual release status from nested locks.
>  
> 0002-Add-new-files-for-OMPT.patch[4]
> This patch contains the new files for OMPT and the needed changes to the build infrastructure.
>  
> 0003-Modify-runtime-to-call-correct-functions-for-OMPT.patch[5]
> These are the actual changes in the runtime to issue OMPT-related functions.
> All of them are surrounded by #if OMPT_SUPPORT and can be disabled (which is the default).
>  
> The implementation is tested with the OMPT-TestSuite[6] and conforms with the OpenMP's 2nd Technical Report[1].
> Additionally we ran the OpenMP Validation Suite contained in this repository to make sure that nothing broke.
>  
> Please review and commit if found suitable.
> We know that these are rather big patches (for a big feature), but we couldn't come up with a better splitting.
>  
> From Aachen,
> Tim Cramer and Jonas Hahnfeld
>  
> [1]: http://openmp.org/mp-documents/ompt-tr2.pdf <http://openmp.org/mp-documents/ompt-tr2.pdf>
> [2]: https://code.google.com/p/ompt-intel-openmp/ <https://code.google.com/p/ompt-intel-openmp/>
> [3]: http://reviews.llvm.org/D8916 <http://reviews.llvm.org/D8916>
> [4]: http://reviews.llvm.org/D8917 <http://reviews.llvm.org/D8917>
> [5]: http://reviews.llvm.org/D8918 <http://reviews.llvm.org/D8918>
> [6]: https://code.google.com/p/ompt-test-suite/ <https://code.google.com/p/ompt-test-suite/>
>  
>  
> --
> Jonas Hahnfeld, MATSE-Auszubildender
>  
> IT Center
> Group: High Performance Computing
> Division: Computational Science and Engineering RWTH Aachen University Seffenter Weg 23 D 52074  Aachen (Germany) Hahnfeld at itc.rwth-aachen.de <mailto:Hahnfeld at itc.rwth-aachen.de>www.itc.rwth-aachen.de <http://www.itc.rwth-aachen.de/>
>  
>  
>  
> 
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