Bug 1868629 - Don't attempt to recover from failure when creating GC markers for the first time r=sfink

The recovery behaviour was added so that attempting to enable parallel marking
by setting a GC parameter didn't cause a hard failure if there was an
allocation failure initializing the extra markers. However the change made it
so we would ignore failing to allocate the first marker (required) on
initialization.

This would have been caught by the OOM test we have for creating contexts, but
this uses the 'always fail' OOM injection mode. This means that an earlier
unhandled OOM condtions can be masked by a later one that is handled. For peace
of mind I changed the test to run in both single failure and permanent failure
modes.

Differential Revision: https://phabricator.services.mozilla.com/D195770

Author: jonco3

js/src/gc/GC.cpp

@@ -833,7 +833,9 @@ bool GCRuntime::init(uint32_t maxbytes) {
   }
 #endif
 
-  initOrDisableParallelMarking();
+  if (!updateMarkersVector()) {
+    return false;
+  }
 
   {
     AutoLockGCBgAlloc lock(this);
@@ -1334,6 +1336,8 @@ void GCRuntime::assertNoMarkingWork() const {
 bool GCRuntime::initOrDisableParallelMarking() {
   // Attempt to initialize parallel marking state or disable it on failure.
 
+  MOZ_ASSERT(markers.length() != 0);
+
   if (!updateMarkersVector()) {
     parallelMarkingEnabled = false;
     return false;

js/src/jsapi-tests/testOOM.cpp

@@ -33,22 +33,25 @@ END_TEST(testOOM)
 
 const uint32_t maxAllocsPerTest = 100;
 
-#  define START_OOM_TEST(name)                                    \
-    testName = name;                                              \
-    printf("Test %s: started: ", testName);                       \
-    for (oomAfter = 1; oomAfter < maxAllocsPerTest; ++oomAfter) { \
-      js::oom::simulator.simulateFailureAfter(                    \
-          js::oom::FailureSimulator::Kind::OOM, oomAfter,         \
-          js::THREAD_TYPE_MAIN, true)
-
-#  define END_OOM_TEST                                                       \
-    if (!js::oom::HadSimulatedOOM()) {                                       \
-      printf("\nTest %s: finished with %" PRIu64 " allocations\n", testName, \
-             oomAfter - 1);                                                  \
-      break;                                                                 \
-    }                                                                        \
-    }                                                                        \
-    js::oom::simulator.reset();                                              \
+#  define START_OOM_TEST(name)                                      \
+    testName = name;                                                \
+    for (bool always : {false, true}) {                             \
+      const char* subTest = always ? "fail always" : "fail once";   \
+      printf("Test %s (%s): started: ", testName, subTest);         \
+      for (oomAfter = 1; oomAfter < maxAllocsPerTest; ++oomAfter) { \
+        js::oom::simulator.simulateFailureAfter(                    \
+            js::oom::FailureSimulator::Kind::OOM, oomAfter,         \
+            js::THREAD_TYPE_MAIN, always)
+
+#  define END_OOM_TEST                                                  \
+    if (!js::oom::HadSimulatedOOM()) {                                  \
+      printf("\nTest %s (%s): finished with %" PRIu64 " allocations\n", \
+             testName, subTest, oomAfter - 1);                          \
+      break;                                                            \
+    }                                                                   \
+    }                                                                   \
+    }                                                                   \
+    js::oom::simulator.reset();                                         \
     CHECK(oomAfter != maxAllocsPerTest)
 
 #  define MARK_STAR printf("*");