Bug 731094 - Expose a testing function that permits only deterministic GCs (r=igor)

js/src/builtin/TestingFunctions.cpp

@@ -8,6 +8,7 @@
 #include "jscntxt.h"
 #include "jscompartment.h"
 #include "jsfriendapi.h"
+#include "jsgc.h"
 #include "jsobj.h"
 #include "jsprf.h"
 #include "jswrapper.h"
@@ -221,6 +222,19 @@ GCSlice(JSContext *cx, unsigned argc, jsval *vp)
     *vp = JSVAL_VOID;
     return JS_TRUE;
 }
+
+static JSBool
+DeterministicGC(JSContext *cx, unsigned argc, jsval *vp)
+{
+    if (argc != 1) {
+        ReportUsageError(cx, &JS_CALLEE(cx, vp).toObject(), "Wrong number of arguments");
+        return JS_FALSE;
+    }
+
+    gc::SetDeterministicGC(cx, js_ValueToBoolean(vp[2]));
+    *vp = JSVAL_VOID;
+    return JS_TRUE;
+}
 #endif /* JS_GC_ZEAL */
 
 typedef struct JSCountHeapNode JSCountHeapNode;
@@ -516,6 +530,10 @@ static JSFunctionSpecWithHelp TestingFunctions[] = {
     JS_FN_HELP("gcslice", GCSlice, 1, 0,
 "gcslice(n)",
 "  Run an incremental GC slice that marks about n objects."),
+
+    JS_FN_HELP("deterministicgc", DeterministicGC, 1, 0,
+"deterministicgc(true|false)",
+"  If true, only allow determinstic GCs to run."),
 #endif
 
     JS_FN_HELP("internalConst", InternalConst, 1, 0,

js/src/jsapi.cpp

@@ -753,6 +753,7 @@ JSRuntime::JSRuntime()
     gcZealFrequency(0),
     gcNextScheduled(0),
     gcDebugCompartmentGC(false),
+    gcDeterministicOnly(false),
 #endif
     gcCallback(NULL),
     gcSliceCallback(NULL),

js/src/jscntxt.h

@@ -419,6 +419,7 @@ struct JSRuntime : js::RuntimeFriendFields
     int                 gcZealFrequency;
     int                 gcNextScheduled;
     bool                gcDebugCompartmentGC;
+    bool                gcDeterministicOnly;
 
     int gcZeal() { return gcZeal_; }
 

js/src/jsfriendapi.h

@@ -673,7 +673,7 @@ SizeOfJSContext();
     D(LAST_DITCH)                               \
     D(TOO_MUCH_MALLOC)                          \
     D(ALLOC_TRIGGER)                            \
-    D(UNUSED1) /* was CHUNK */                  \
+    D(DEBUG_GC)                                 \
     D(UNUSED2) /* was SHAPE */                  \
     D(UNUSED3) /* was REFILL */                 \
                                                 \

js/src/jsgc.cpp

@@ -1708,13 +1708,13 @@ ArenaLists::finalizeScripts(JSContext *cx)
 }
 
 static void
-RunLastDitchGC(JSContext *cx)
+RunLastDitchGC(JSContext *cx, gcreason::Reason reason)
 {
     JSRuntime *rt = cx->runtime;
 
     /* The last ditch GC preserves all atoms. */
     AutoKeepAtoms keep(rt);
-    GC(cx, rt->gcTriggerCompartment, GC_NORMAL, gcreason::LAST_DITCH);
+    GC(cx, rt->gcTriggerCompartment, GC_NORMAL, reason);
 }
 
 /* static */ void *
@@ -1729,7 +1729,7 @@ ArenaLists::refillFreeList(JSContext *cx, AllocKind thingKind)
     bool runGC = rt->gcIncrementalState != NO_INCREMENTAL && comp->gcBytes > comp->gcTriggerBytes;
     for (;;) {
         if (JS_UNLIKELY(runGC)) {
-            RunLastDitchGC(cx);
+            RunLastDitchGC(cx, gcreason::LAST_DITCH);
 
             /*
              * The JSGC_END callback can legitimately allocate new GC
@@ -3662,6 +3662,20 @@ GCCycle(JSContext *cx, JSCompartment *comp, int64_t budget, JSGCInvocationKind g
 #endif
 }
 
+#ifdef JS_GC_ZEAL
+static bool
+IsDeterministicGCReason(gcreason::Reason reason)
+{
+    if (reason > gcreason::DEBUG_GC && reason != gcreason::CC_FORCED)
+        return false;
+
+    if (reason == gcreason::MAYBEGC)
+        return false;
+
+    return true;
+}
+#endif
+
 static void
 Collect(JSContext *cx, JSCompartment *comp, int64_t budget,
         JSGCInvocationKind gckind, gcreason::Reason reason)
@@ -3669,6 +3683,11 @@ Collect(JSContext *cx, JSCompartment *comp, int64_t budget,
     JSRuntime *rt = cx->runtime;
     JS_AbortIfWrongThread(rt);
 
+#ifdef JS_GC_ZEAL
+    if (rt->gcDeterministicOnly && !IsDeterministicGCReason(reason))
+        return;
+#endif
+
     JS_ASSERT_IF(budget != SliceBudget::Unlimited, JSGC_INCREMENTAL);
 
 #ifdef JS_GC_ZEAL
@@ -3947,7 +3966,16 @@ RunDebugGC(JSContext *cx)
     if (rt->gcTriggerCompartment == rt->atomsCompartment)
         rt->gcTriggerCompartment = NULL;
 
-    RunLastDitchGC(cx);
+    RunLastDitchGC(cx, gcreason::DEBUG_GC);
+#endif
+}
+
+void
+SetDeterministicGC(JSContext *cx, bool enabled)
+{
+#ifdef JS_GC_ZEAL
+    JSRuntime *rt = cx->runtime;
+    rt->gcDeterministicOnly = enabled;
 #endif
 }
 

js/src/jsgc.h

@@ -1968,6 +1968,9 @@ NewCompartment(JSContext *cx, JSPrincipals *principals);
 void
 RunDebugGC(JSContext *cx);
 
+void
+SetDeterministicGC(JSContext *cx, bool enabled);
+
 #if defined(JSGC_ROOT_ANALYSIS) && defined(DEBUG) && !defined(JS_THREADSAFE)
 /* Overwrites stack references to GC things which have not been rooted. */
 void CheckStackRoots(JSContext *cx);