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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>I agree with you Reid on creating temp files.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal>>In this case, llc will dump lots of text to stderr, which is piped to lit. That buffer will fill and writes will block. lit will 'communicate' with FileCheck, and no progress will be made<span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>I was exactly trying to convey this.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D'>--Sumanth G<o:p></o:p></span></p><p class=MsoNormal><b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'>From:</span></b><span style='font-size:11.0pt;font-family:"Calibri",sans-serif'> Reid Kleckner [mailto:rnk@google.com] <br><b>Sent:</b> Monday, January 26, 2015 1:32 PM<br><b>To:</b> Sumanth Gundapaneni<br><b>Cc:</b> LLVM Developers Mailing List<br><b>Subject:</b> Re: [LLVMdev] Deadlock in llvm-lit on windows 7<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>Honestly, lit should just create temp files and get out of the business of polling and reading from subprocess pipes.<o:p></o:p></p><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>I think you have more or less diagnosed the problem, with the caveat that communicate will not block because the underlying pipes of that process are full. It is more likely that some other process is blocked writing to a full pipe, and the process under communication is also waiting on that pipe. Consider this pipeline:<o:p></o:p></p></div><div><p class=MsoNormal> llc -debug -mtriple=x86_64-linux < %s | FileCheck %s<o:p></o:p></p></div><div><p class=MsoNormal><o:p> </o:p></p></div><div><p class=MsoNormal>In this case, llc will dump lots of text to stderr, which is piped to lit. That buffer will fill and writes will block. lit will 'communicate' with FileCheck, and no progress will be made.<o:p></o:p></p></div></div><div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal>On Mon, Jan 26, 2015 at 9:57 AM, Sumanth Gundapaneni <<a href="mailto:sgundapa@codeaurora.org" target="_blank">sgundapa@codeaurora.org</a>> wrote:<o:p></o:p></p><blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0in 0in 0in 6.0pt;margin-left:4.8pt;margin-right:0in'><div><div><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Hi,<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> I am observing a deadlock with llvm-lit on windows 7.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>When I attached a debugger, the communicate() call is blocked.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>In file utils/lit/lit/TestRunner.py<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> # FIXME: There is probably still deadlock potential here. Yawn.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> procData = [None] * len(procs)<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>> procData[-1] = procs[-1].communicate()<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>I am invoking python directly on windows to run the unit tests. <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>C:\Python27\python.exe C:\build\llvm\Release\bin\llvm-lit.py -v -j 12 --param build_mode=Release --param build_config=Win32 llvm_site_config=C:\llvm_on_win\nightly\build\llvm\tools\polly\test\lit.site.cfg test<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Note: If I invoke with “-j 1” , the unit tests finish but took a lot of time. There is no deadlock. I am using python version 2.7.6.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>At this moment, I believe the issue is caused by stdout filling the OS buffer there by blocking the communicate() call.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>It is possible some of the unit tests dump a lot of text/data to stdout. FYI, I have a couple of unit tests of my own in the code base.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>On Linux, there is no deadlock but on windows I am hitting a deadlock 7 out of 10 times. I tried invoking python with “-u” but in vain.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>When I looked at llvm-lit code, I saw the code to avoid deadlocks but there was no guarantee, like the one I pasted above.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>Would appreciate if some one take a look at it and provide more context on deadlocks.<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'>--Sumanth G<o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p><p class=MsoNormal style='mso-margin-top-alt:auto;mso-margin-bottom-alt:auto'> <o:p></o:p></p></div></div><p class=MsoNormal style='margin-bottom:12.0pt'><br>_______________________________________________<br>LLVM Developers mailing list<br><a href="mailto:LLVMdev@cs.uiuc.edu">LLVMdev@cs.uiuc.edu</a> <a href="http://llvm.cs.uiuc.edu" target="_blank">http://llvm.cs.uiuc.edu</a><br><a href="http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev" target="_blank">http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev</a><o:p></o:p></p></blockquote></div><p class=MsoNormal><o:p> </o:p></p></div></div></body></html>