SIGSEGV in ompt_tsan_dependences with for-ordered

[RitanyaB]

Summary

Segmentation fault in ompt_tsan_dependences function due to an unchecked NULL pointer dereference is as follows:

ThreadSanitizer:DEADLYSIGNAL
	==140865==ERROR: ThreadSanitizer: SEGV on unknown address 0x000000000050 (pc 0x7f217c2d3652 bp 0x7ffe8cfc7e00 sp 0x7ffe8cfc7d90 T140865)
	==140865==The signal is caused by a READ memory access.
	==140865==Hint: address points to the zero page.
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 1012a
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 133b5
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 1371a
	/usr/bin/addr2line: DWARF error: could not find variable specification at offset 13a58
	#0 ompt_tsan_dependences(ompt_data_t*, ompt_dependence_t const*, int) /ptmp/bhararit/llvm-project/openmp/tools/archer/ompt-tsan.cpp:1004 (libarcher.so+0x15652)
	#1 __kmpc_doacross_post /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_csupport.cpp:4280 (libomp.so+0x74d98)
	#2 .omp_outlined. for_ordered_01.c:? (for_ordered_01.exe+0x5186cb)
	#3 __kmp_invoke_microtask /ptmp/bhararit/llvm-project/openmp/runtime/src/z_Linux_asm.S:1166 (libomp.so+0x14e592)
	#4 __kmp_invoke_task_func /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_runtime.cpp:7556 (libomp.so+0x909ad)
	#5 __kmp_fork_call /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_runtime.cpp:2284 (libomp.so+0x8461a)
	#6 __kmpc_fork_call /ptmp/bhararit/llvm-project/openmp/runtime/src/kmp_csupport.cpp:308 (libomp.so+0x6db55)
	#7 main ??:? (for_ordered_01.exe+0x51828f)
	#8 __libc_start_main ??:? (libc.so.6+0x24349)
	#9 _start /home/abuild/rpmbuild/BUILD/glibc-2.26/csu/../sysdeps/x86_64/start.S:120 (for_ordered_01.exe+0x4214e9)
	
	ThreadSanitizer can not provide additional info.
	SUMMARY: ThreadSanitizer: SEGV /ptmp/bhararit/llvm-project/openmp/tools/archer/ompt-tsan.cpp:1004 in ompt_tsan_dependences(ompt_data_t*, ompt_dependence_t const*, int)
	==140865==ABORTING

To reproduce the error, use the following openmp code snippet:

/* initialise  testMatrixInt Matrix, cols, r and c */
	  #pragma omp parallel private(r,c) shared(testMatrixInt)
	    {
	      #pragma omp for ordered(2)
	      for (r=1; r < rows; r++) {
	        for (c=1; c < cols; c++) {
	          #pragma omp ordered depend(sink:r-1, c+1) depend(sink:r-1,c-1)
	          testMatrixInt[r][c] = (testMatrixInt[r-1][c] + testMatrixInt[r-1][c-1]) % cols ;
	          #pragma omp ordered depend (source)
	        }
	      }
	    }

Compilation:

clang -g -stdlib=libc++ -fsanitize=thread -fopenmp -larcher test_case.c

It seems like the changes introduced by the commit https://reviews.llvm.org/D114005 causes this particular SEGV while using Archer.

[protze.joachim]

Just return, if (Data->Parent == nullptr).

The actual issue is that doacross dependences is not yet supported.

[protze.joachim]

Thanks for the update. LGTM.
Can you commit yourself, or should I commit the fix for you?

[RitanyaB]

In D115328#3195018, @protze.joachim wrote:

Thanks for the update. LGTM.
Can you commit yourself, or should I commit the fix for you?

Since I do not have write permission, could you grant me commit access? If not, can you please commit the fix for me?
Thanks.

openmp/tools/archer/ompt-tsan.cpp

static void ompt_tsan_task_schedule(ompt_data_t *first_task_data,
   TsanHappensAfter(ToTask->GetTaskPtr());
 }
 
 static void ompt_tsan_dependences(ompt_data_t *task_data,
                                   const ompt_dependence_t *deps, int ndeps) {
   if (ndeps > 0) {
     // Copy the data to use it in task_switch and task_end.
     TaskData *Data = ToTaskData(task_data);
+    if (!Data->Parent) {
+      // Return since doacross dependences are not supported yet.
+      return;
+    }
     if (!Data->Parent->DependencyMap)
       Data->Parent->DependencyMap =
           new std::unordered_map<void *, DependencyData *>();
     Data->Dependencies =
         (TaskDependency *)malloc(sizeof(TaskDependency) * ndeps);
     Data->DependencyCount = ndeps;
     for (int i = 0; i < ndeps; i++) {
       auto ret = Data->Parent->DependencyMap->insert(