[llvm] r269588 - ThinLTOCodeGenerator: fix race condition found using TSAN

Mehdi Amini via llvm-commits llvm-commits at lists.llvm.org
Mon May 16 10:35:54 PDT 2016


> On May 16, 2016, at 10:30 AM, Kostya Serebryany <kcc at google.com> wrote:
> 
> 
> 
> 
> On Mon, May 16, 2016 at 10:25 AM, Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>> wrote:
> 
>> On May 16, 2016, at 10:22 AM, Kostya Serebryany <kcc at google.com <mailto:kcc at google.com>> wrote:
>> 
>> Nice! 
>> What exactly did you run under than? 
> 
> Bootstrap clang with ThinLTO.
> 
>> Is this is something like "ninja check-foo" (check-thin-lto?), I'd like to add this to our sanitizer bot. 
> 
> I plan to add a bot that performs TSAN bootstrap with ThinLTO, probably in a month.
> 
> Excellent! 
> Are you going to set up your own bot? 

Yes, I plan to add it to our jobs here: http://lab.llvm.org:8080/green/


> We already have an asan/msan bootstrap bot: zorg/buildbot/builders/sanitizers/buildbot_bootstrap.sh
> Although adding tsan to this bot will make it too slow, we probably better have a separate one. 

I noticed that TSAN has some noticeable overhead (particularly memory overhead)

-- 
Mehdi


> 
> --kcc 
>  
> Right is it a bit challenging. Even though we could add a few llvm-lto tests that would run with threads, this would require an artificially large amount of input files to exhibit the races, not sure if there is a good way for that.
> 
> 
>  
> 
> -- 
> Mehdi
> 
> 
> 
>> 
>> On Sat, May 14, 2016 at 10:49 PM, Mehdi Amini via llvm-commits <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
>> Author: mehdi_amini
>> Date: Sun May 15 00:49:47 2016
>> New Revision: 269588
>> 
>> URL: http://llvm.org/viewvc/llvm-project?rev=269588&view=rev <http://llvm.org/viewvc/llvm-project?rev=269588&view=rev>
>> Log:
>> ThinLTOCodeGenerator: fix race condition found using TSAN
>> 
>> From: Mehdi Amini <mehdi.amini at apple.com <mailto:mehdi.amini at apple.com>>
>> 
>> Modified:
>>     llvm/trunk/lib/LTO/ThinLTOCodeGenerator.cpp
>> 
>> Modified: llvm/trunk/lib/LTO/ThinLTOCodeGenerator.cpp
>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/LTO/ThinLTOCodeGenerator.cpp?rev=269588&r1=269587&r2=269588&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/LTO/ThinLTOCodeGenerator.cpp?rev=269588&r1=269587&r2=269588&view=diff>
>> ==============================================================================
>> --- llvm/trunk/lib/LTO/ThinLTOCodeGenerator.cpp (original)
>> +++ llvm/trunk/lib/LTO/ThinLTOCodeGenerator.cpp Sun May 15 00:49:47 2016
>> @@ -884,6 +884,11 @@ void ThinLTOCodeGenerator::run() {
>>    auto GUIDPreservedSymbols =
>>        computeGUIDPreservedSymbols(PreservedSymbols, TMBuilder.TheTriple);
>> 
>> +  // Make sure that every module has an entry in the ExportLists to enable
>> +  // threaded access to this map below
>> +  for (auto &DefinedGVSummaries : ModuleToDefinedGVSummaries)
>> +    ExportLists[DefinedGVSummaries.first()];
>> +
>>    // Parallel optimizer + codegen
>>    {
>>      ThreadPool Pool(ThreadCount);
>> 
>> 
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