Nischai Vinesh via llvm-dev
2017-Jul-10 11:06 UTC
[llvm-dev] Using TSAN along with custom llvm IR pass
I think the code is not getting instrumented with tsan at all. In the 'step 3', when I instrument it using 'opt -tsan ...', it gives a warning "WARNING: You're attempting to print out a bitcode file." I guess this method doesn't instrument the code. Is there any other way I can instrument the code with tsan? On Monday, July 10, 2017 at 7:21:28 AM UTC+2, Dmitry Vyukov wrote:> > On Sun, Jul 9, 2017 at 3:50 PM, Nischai Vinesh <nischai... at gmail.com > <javascript:>> wrote: > > Hello, > > > > I tried that as well but there are no tsan warnings thrown at run time, > even > > though there are data race error! > > > > The steps I followed: > > 1. Generate bitcode using 'clang -emit-llvm' command > > 2. Using the 'opt -load ..' command, I instrumented the bitcode file > with my > > custom pass > > 3. Using the command 'opt -tsan ..', instrumented the output bitcode > file > > from step 2 > > 4. Using the llvm backend compiler, 'llc', compiled the program to > native > > assembly > > 5. The output from step 4 is compiled again with 'clang > -fsanitize=thread' > > (linking tsan here) for the final object file. > > > > Executing this final output file works fine, except that it doesn't > throws > > any TSAN warnings! > > > Hi Nischai, > > I see 3 possibilities: > 1. Either the code is somehow ends up being non-instrumented, or > 2. tsan does not consider what it sees a data race, or > 3. the data race is masked by unrelated synchronization. > > For 1 you can check that the resulting code in fact contains __tsan_* > callbacks. > For 2 and 3 you can rebuilt tsan runtime with TSAN_DEBUG_OUTPUT=2 > define, then it will print everything it sees (memory accesses and > synchronization). This output will allow us to figure out why it does > not report a race. >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170710/948f690d/attachment.html>
Nischai Vinesh via llvm-dev
2017-Jul-10 13:00 UTC
[llvm-dev] Using TSAN along with custom llvm IR pass
Oh ok. But is there any dependency when I change to this method, other than the way the pass is registered? Because when I used clang along with -Xclang to run the pass on the program, it is crashing! On Monday, July 10, 2017 at 1:09:43 PM UTC+2, Dmitry Vyukov wrote:> > On Mon, Jul 10, 2017 at 1:06 PM, Nischai Vinesh > <nischai... at gmail.com <javascript:>> wrote: > > I think the code is not getting instrumented with tsan at all. In the > 'step > > 3', when I instrument it using 'opt -tsan ...', it gives a warning > "WARNING: > > You're attempting to print out a bitcode file." I guess this method > doesn't > > instrument the code. > > > > Is there any other way I can instrument the code with tsan? > > > One option is to add your pass to llvm and execute clang with > -fsanitize=thread. > > > > On Monday, July 10, 2017 at 7:21:28 AM UTC+2, Dmitry Vyukov wrote: > >> > >> On Sun, Jul 9, 2017 at 3:50 PM, Nischai Vinesh <nischai... at gmail.com> > >> wrote: > >> > Hello, > >> > > >> > I tried that as well but there are no tsan warnings thrown at run > time, > >> > even > >> > though there are data race error! > >> > > >> > The steps I followed: > >> > 1. Generate bitcode using 'clang -emit-llvm' command > >> > 2. Using the 'opt -load ..' command, I instrumented the bitcode file > >> > with my > >> > custom pass > >> > 3. Using the command 'opt -tsan ..', instrumented the output bitcode > >> > file > >> > from step 2 > >> > 4. Using the llvm backend compiler, 'llc', compiled the program to > >> > native > >> > assembly > >> > 5. The output from step 4 is compiled again with 'clang > >> > -fsanitize=thread' > >> > (linking tsan here) for the final object file. > >> > > >> > Executing this final output file works fine, except that it doesn't > >> > throws > >> > any TSAN warnings! > >> > >> > >> Hi Nischai, > >> > >> I see 3 possibilities: > >> 1. Either the code is somehow ends up being non-instrumented, or > >> 2. tsan does not consider what it sees a data race, or > >> 3. the data race is masked by unrelated synchronization. > >> > >> For 1 you can check that the resulting code in fact contains __tsan_* > >> callbacks. > >> For 2 and 3 you can rebuilt tsan runtime with TSAN_DEBUG_OUTPUT=2 > >> define, then it will print everything it sees (memory accesses and > >> synchronization). This output will allow us to figure out why it does > >> not report a race. > > > > -- > > You received this message because you are subscribed to the Google > Groups > > "thread-sanitizer" group. > > To unsubscribe from this group and stop receiving emails from it, send > an > > email to thread-sanitiz... at googlegroups.com <javascript:>. > > For more options, visit https://groups.google.com/d/optout. >-------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20170710/3f13e765/attachment.html>