[libFuzzer] make shmem more robust in the presence of signals

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@293339 91177308-0d34-0410-b5e6-96231b3b80d8

Author: kcc

lib/Fuzzer/FuzzerShmemPosix.cpp

@@ -86,9 +86,13 @@ void SharedMemoryRegion::Post(int Idx) {
 
 void SharedMemoryRegion::Wait(int Idx) {
   assert(Idx == 0 || Idx == 1);
-  if (sem_wait((sem_t*)Semaphore[Idx])) {
-    Printf("ERROR: sem_wait failed\n");
-    exit(1);
+  for (int i = 0; i < 10 && sem_wait((sem_t*)Semaphore[Idx]); i++) {
+    // sem_wait may fail if interrupted by a signal.
+    sleep(i);
+    if (i)
+      Printf("%s: sem_wait[%d] failed %s\n", i < 9 ? "WARNING" : "ERROR", i,
+             strerror(errno));
+    if (i == 9) abort();
   }
 }
 

lib/Fuzzer/test/equivalence.test

@@ -4,3 +4,13 @@ RUN: not LLVMFuzzer-EquivalenceBTest -use_equivalence_server=EQUIV_TEST 2>&1 | F
 CHECK: ERROR: libFuzzer: equivalence-mismatch. Sizes: {{.*}}; offset 2
 CHECK: SUMMARY: libFuzzer: equivalence-mismatch
 RUN: kill -9 $APID
+
+
+# Run EquivalenceATest against itself with a small timeout
+# to stress the signal handling and ensure that shmem doesn't mind
+# the signals.
+
+RUN: LLVMFuzzer-EquivalenceATest -timeout=1 -run_equivalence_server=EQUIV_TEST & export APID=$!
+RUN: sleep 3
+RUN: LLVMFuzzer-EquivalenceATest -timeout=1 -use_equivalence_server=EQUIV_TEST -runs=500000 2>&1
+RUN: kill -9 $APID