kfdtest: fix ptrace error on multi-gpu mode

The parent process can only be ptraced by 1 process
once, to avoid the error we have to add mutex to
synchronize the ptrace call.

Signed-off-by: Eric Huang <jinhuieric.huang@amd.com>


[ROCm/ROCR-Runtime commit: d3265234e9]

projects/rocr-runtime/libhsakmt/tests/kfdtest/src/KFDMemoryTest.cpp

@@ -42,6 +42,8 @@
 /* Captures user specified time (seconds) to sleep */
 extern unsigned int g_SleepTime;
 
+static pthread_mutex_t ptrace_mtx;
+
 void KFDMemoryTest::SetUp() {
     ROUTINE_START
 
@@ -1353,6 +1355,8 @@ static void PtraceAccess(KFDTEST_PARAMETERS* pTestParamters) {
     prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0);
 #endif
 
+    pthread_mutex_lock(&ptrace_mtx);
+
     // Find current pid so the child can trace it
     pid_t tracePid = getpid();
 
@@ -1414,6 +1418,8 @@ static void PtraceAccess(KFDTEST_PARAMETERS* pTestParamters) {
         EXPECT_EQ_GPU(0, WEXITSTATUS(childStatus), gpuNode);
     }
 
+    pthread_mutex_unlock(&ptrace_mtx);
+
     // Clear gaps in the source that should not have been copied
     (reinterpret_cast<uint8_t*>(mem[0]))[  sizeof(long)    ] = 0;
     (reinterpret_cast<uint8_t*>(mem[0]))[2*sizeof(long) + 1] = 0;
@@ -1508,6 +1514,8 @@ static void PtraceAccessInvisibleVram(KFDTEST_PARAMETERS* pTestParamters) {
     prctl(PR_SET_PTRACER, PR_SET_PTRACER_ANY, 0, 0, 0);
 #endif
 
+    pthread_mutex_lock(&ptrace_mtx);
+
     // Find out my pid so the child can trace it
     pid_t tracePid = getpid();
 
@@ -1564,6 +1572,8 @@ static void PtraceAccessInvisibleVram(KFDTEST_PARAMETERS* pTestParamters) {
         EXPECT_EQ_GPU(0, WEXITSTATUS(childStatus), gpuNode);
     }
 
+    pthread_mutex_unlock(&ptrace_mtx);
+
     /* Use shader to read back data to check poke results */
     HsaMemoryBuffer isaBuffer(PAGE_SIZE, gpuNode, true/*zero*/, false/*local*/, true/*exec*/);
     // dstBuffer is cpu accessible gtt memory