jsgc.c

java script test programing source code

     * protect against GC that the hook can trigger.
     */
    fp = cx->fp;
    if (fp) {
        JS_ASSERT(!fp->dormantNext);
        fp->dormantNext = cx->dormantFrameChain;
        cx->dormantFrameChain = fp;
    }
    cx->fp = NULL;

    genp = &tempList.head;
    ok = JS_TRUE;
    while ((gen = *genp) != NULL) {
        ok = ShouldDeferCloseHook(cx, gen, &defer);
        if (!ok) {
            /* Quit ASAP discarding the hook. */
            *genp = gen->next;
            break;
        }
        if (defer) {
            genp = &gen->next;
            METER(deferCount++);
            continue;
        }
        ok = js_CloseGeneratorObject(cx, gen);

        /*
         * Unlink the generator after closing it to make sure it always stays
         * rooted through tempList.
         */
        *genp = gen->next;

        if (cx->throwing) {
            /*
             * Report the exception thrown by the close hook and continue to
             * execute the rest of the hooks.
             */
            if (!js_ReportUncaughtException(cx))
                JS_ClearPendingException(cx);
            ok = JS_TRUE;
        } else if (!ok) {
            /*
             * Assume this is a stop signal from the branch callback or
             * other quit ASAP condition. Break execution until the next
             * invocation of js_RunCloseHooks.
             */
            break;
        }
    }

    cx->fp = fp;
    if (fp) {
        JS_ASSERT(cx->dormantFrameChain == fp);
        cx->dormantFrameChain = fp->dormantNext;
        fp->dormantNext = NULL;
    }

    if (tempList.head) {
        /*
         * Some close hooks were not yet executed, put them back into the
         * scheduled list.
         */
        while ((gen = *genp) != NULL) {
            genp = &gen->next;
            METER(deferCount++);
        }

        /* Now genp is a pointer to the tail of tempList. */
        JS_LOCK_GC(rt);
        *genp = rt->gcCloseState.todoQueue;
        rt->gcCloseState.todoQueue = tempList.head;
        METER(rt->gcStats.closelater += deferCount);
        METER(rt->gcStats.maxcloselater
              = JS_MAX(rt->gcStats.maxcloselater, rt->gcStats.closelater));
        JS_UNLOCK_GC(rt);
    }

    JS_POP_TEMP_CLOSE_LIST(cx, &tempList);
    *GC_RUNNING_CLOSE_HOOKS_PTR(cx) = JS_FALSE;

    return ok;
}

#endif /* JS_HAS_GENERATORS */

#if defined(DEBUG_brendan) || defined(DEBUG_timeless)
#define DEBUG_gchist
#endif

#ifdef DEBUG_gchist
#define NGCHIST 64

static struct GCHist {
    JSBool      lastDitch;
    JSGCThing   *freeList;
} gchist[NGCHIST];

unsigned gchpos;
#endif

void *
js_NewGCThing(JSContext *cx, uintN flags, size_t nbytes)
{
    JSRuntime *rt;
    uintN flindex;
    JSBool doGC;
    JSGCThing *thing;
    uint8 *flagp, *firstPage;
    JSGCArenaList *arenaList;
    jsuword offset;
    JSGCArena *a;
    JSLocalRootStack *lrs;
#ifdef JS_THREADSAFE
    JSBool gcLocked;
    uintN localMallocBytes;
    JSGCThing **flbase, **lastptr;
    JSGCThing *tmpthing;
    uint8 *tmpflagp;
    uintN maxFreeThings;         /* max to take from the global free list */
    METER(size_t nfree);
#endif

    rt = cx->runtime;
    METER(rt->gcStats.alloc++);        /* this is not thread-safe */
    nbytes = JS_ROUNDUP(nbytes, sizeof(JSGCThing));
    flindex = GC_FREELIST_INDEX(nbytes);

#ifdef JS_THREADSAFE
    gcLocked = JS_FALSE;
    JS_ASSERT(cx->thread);
    flbase = cx->thread->gcFreeLists;
    JS_ASSERT(flbase);
    thing = flbase[flindex];
    localMallocBytes = cx->thread->gcMallocBytes;
    if (thing && rt->gcMaxMallocBytes - rt->gcMallocBytes > localMallocBytes) {
        flagp = thing->flagp;
        flbase[flindex] = thing->next;
        METER(rt->gcStats.localalloc++);  /* this is not thread-safe */
        goto success;
    }

    JS_LOCK_GC(rt);
    gcLocked = JS_TRUE;

    /* Transfer thread-local counter to global one. */
    if (localMallocBytes != 0) {
        cx->thread->gcMallocBytes = 0;
        if (rt->gcMaxMallocBytes - rt->gcMallocBytes < localMallocBytes)
            rt->gcMallocBytes = rt->gcMaxMallocBytes;
        else
            rt->gcMallocBytes += localMallocBytes;
    }
#endif
    JS_ASSERT(!rt->gcRunning);
    if (rt->gcRunning) {
        METER(rt->gcStats.finalfail++);
        JS_UNLOCK_GC(rt);
        return NULL;
    }

#ifdef TOO_MUCH_GC
#ifdef WAY_TOO_MUCH_GC
    rt->gcPoke = JS_TRUE;
#endif
    doGC = JS_TRUE;
#else
    doGC = (rt->gcMallocBytes >= rt->gcMaxMallocBytes);
#endif

    arenaList = &rt->gcArenaList[flindex];
    for (;;) {
        if (doGC) {
            /*
             * Keep rt->gcLock across the call into js_GC so we don't starve
             * and lose to racing threads who deplete the heap just after
             * js_GC has replenished it (or has synchronized with a racing
             * GC that collected a bunch of garbage).  This unfair scheduling
             * can happen on certain operating systems. For the gory details,
             * see bug 162779 at https://bugzilla.mozilla.org/.
             */
            js_GC(cx, GC_LAST_DITCH);
            METER(rt->gcStats.retry++);
        }

        /* Try to get thing from the free list. */
        thing = arenaList->freeList;
        if (thing) {
            arenaList->freeList = thing->next;
            flagp = thing->flagp;
            JS_ASSERT(*flagp & GCF_FINAL);
            METER(arenaList->stats.freelen--);
            METER(arenaList->stats.recycle++);

#ifdef JS_THREADSAFE
            /*
             * Refill the local free list by taking several things from the
             * global free list unless we are still at rt->gcMaxMallocBytes
             * barrier or the free list is already populated. The former
             * happens when GC is canceled due to !gcCallback(cx, JSGC_BEGIN)
             * or no gcPoke. The latter is caused via allocating new things
             * in gcCallback(cx, JSGC_END).
             */
            if (rt->gcMallocBytes >= rt->gcMaxMallocBytes || flbase[flindex])
                break;
            tmpthing = arenaList->freeList;
            if (tmpthing) {
                maxFreeThings = MAX_THREAD_LOCAL_THINGS;
                do {
                    if (!tmpthing->next)
                        break;
                    tmpthing = tmpthing->next;
                } while (--maxFreeThings != 0);

                flbase[flindex] = arenaList->freeList;
                arenaList->freeList = tmpthing->next;
                tmpthing->next = NULL;
            }
#endif
            break;
        }

        /* Allocate from the tail of last arena or from new arena if we can. */
        if ((arenaList->last && arenaList->lastLimit != GC_THINGS_SIZE) ||
            NewGCArena(rt, arenaList)) {

            offset = arenaList->lastLimit;
            if ((offset & GC_PAGE_MASK) == 0) {
                /*
                 * Skip JSGCPageInfo record located at GC_PAGE_SIZE boundary.
                 */
                offset += PAGE_THING_GAP(nbytes);
            }
            JS_ASSERT(offset + nbytes <= GC_THINGS_SIZE);
            arenaList->lastLimit = (uint16)(offset + nbytes);
            a = arenaList->last;
            firstPage = (uint8 *)FIRST_THING_PAGE(a);
            thing = (JSGCThing *)(firstPage + offset);
            flagp = a->base + offset / sizeof(JSGCThing);
            if (flagp >= firstPage)
                flagp += GC_THINGS_SIZE;
            METER(++arenaList->stats.nthings);
            METER(arenaList->stats.maxthings =
                  JS_MAX(arenaList->stats.nthings,
                         arenaList->stats.maxthings));

#ifdef JS_THREADSAFE
            /*
             * Refill the local free list by taking free things from the last
             * arena. Prefer to order free things by ascending address in the
             * (unscientific) hope of better cache locality.
             */
            if (rt->gcMallocBytes >= rt->gcMaxMallocBytes || flbase[flindex])
                break;
            METER(nfree = 0);
            lastptr = &flbase[flindex];
            maxFreeThings = MAX_THREAD_LOCAL_THINGS;
            for (offset = arenaList->lastLimit;
                 offset != GC_THINGS_SIZE && maxFreeThings-- != 0;
                 offset += nbytes) {
                if ((offset & GC_PAGE_MASK) == 0)
                    offset += PAGE_THING_GAP(nbytes);
                JS_ASSERT(offset + nbytes <= GC_THINGS_SIZE);
                tmpflagp = a->base + offset / sizeof(JSGCThing);
                if (tmpflagp >= firstPage)
                    tmpflagp += GC_THINGS_SIZE;

                tmpthing = (JSGCThing *)(firstPage + offset);
                tmpthing->flagp = tmpflagp;
                *tmpflagp = GCF_FINAL;    /* signifying that thing is free */

                *lastptr = tmpthing;
                lastptr = &tmpthing->next;
                METER(++nfree);
            }
            arenaList->lastLimit = offset;
            *lastptr = NULL;
            METER(arenaList->stats.freelen += nfree);
#endif
            break;
        }

        /* Consider doing a "last ditch" GC unless already tried. */
        if (doGC)
            goto fail;
        rt->gcPoke = JS_TRUE;
        doGC = JS_TRUE;
    }

    /* We successfully allocated the thing. */
#ifdef JS_THREADSAFE
  success:
#endif
    lrs = cx->localRootStack;
    if (lrs) {
        /*
         * If we're in a local root scope, don't set newborn[type] at all, to
         * avoid entraining garbage from it for an unbounded amount of time
         * on this context.  A caller will leave the local root scope and pop
         * this reference, allowing thing to be GC'd if it has no other refs.
         * See JS_EnterLocalRootScope and related APIs.
         */
        if (js_PushLocalRoot(cx, lrs, (jsval) thing) < 0) {
            /*
             * When we fail for a thing allocated through the tail of the last
             * arena, thing's flag byte is not initialized. So to prevent GC
             * accessing the uninitialized flags during the finalization, we
             * always mark the thing as final. See bug 337407.
             */
            *flagp = GCF_FINAL;
            goto fail;
        }
    } else {
        /*
         * No local root scope, so we're stuck with the old, fragile model of
         * depending on a pigeon-hole newborn per type per context.
         */
        cx->weakRoots.newborn[flags & GCF_TYPEMASK] = thing;
    }

    /* We can't fail now, so update flags and rt->gc{,Private}Bytes. */
    *flagp = (uint8)flags;

    /*
     * Clear thing before unlocking in case a GC run is about to scan it,
     * finding it via newborn[].
     */
    thing->next = NULL;
    thing->flagp = NULL;
#ifdef DEBUG_gchist
    gchist[gchpos].lastDitch = doGC;
    gchist[gchpos].freeList = rt->gcArenaList[flindex].freeList;
    if (++gchpos == NGCHIST)
        gchpos = 0;
#endif
    METER(if (flags & GCF_LOCK) rt->gcStats.lockborn++);
    METER(++rt->gcArenaList[flindex].stats.totalnew);
#ifdef JS_THREADSAFE
    if (gcLocked)
        JS_UNLOCK_GC(rt);
#endif
    return thing;

fail:
#ifdef JS_THREADSAFE
    if (gcLocked)
        JS_UNLOCK_GC(rt);
#endif
    METER(rt->gcStats.fail++);
    JS_ReportOutOfMemory(cx);
    return NULL;
}

JSBool
js_LockGCThing(JSContext *cx, void *thing)
{
    JSBool ok = js_LockGCThingRT(cx->runtime, thing);
    if (!ok)
        JS_ReportOutOfMemory(cx);
    return ok;
}

/*
 * Deep GC-things can't be locked just by setting the GCF_LOCK bit, because
 * their descendants must be marked by the GC.  To find them during the mark
 * phase, they are added to rt->gcLocksHash, which is created lazily.
 *
 * NB: we depend on the order of GC-thing type indexes here!
 */
#define GC_TYPE_IS_STRING(t)    ((t) == GCX_STRING ||                         \
                                 (t) >= GCX_EXTERNAL_STRING)
#define GC_TYPE_IS_XML(t)       ((unsigned)((t) - GCX_NAMESPACE) <=           \
                                 (unsigned)(GCX_XML - GCX_NAMESPACE))
#define GC_TYPE_IS_DEEP(t)      ((t) == GCX_OBJECT || GC_TYPE_IS_XML(t))

#define IS_DEEP_STRING(t,o)     (GC_TYPE_IS_STRING(t) &&                      \
                                 JSSTRING_IS_DEPENDENT((JSString *)(o)))

#define GC_THING_IS_DEEP(t,o)   (GC_TYPE_IS_DEEP(t) || IS_DEEP_STRING(t, o))

/* This is compatible with JSDHashEntryStub. */
typedef struct JSGCLockHashEntry {
    JSDHashEntryHdr hdr;
    const JSGCThing *thing;
    uint32          count;
} JSGCLockHashEntry;

JSBool
js_LockGCThingRT(JSRuntime *rt, void *thing)
{
    JSBool ok, deep;
    uint8 *flagp;
    uintN flags, lock, type;
    JSGCLockHashEntry *lhe;

    ok = JS_TRUE;
    if (!thing)
        return ok;

    flagp = js_GetGCThingFlags(thing);

    JS_LOCK_GC(rt);
    flags = *flagp;
    lock = (flags & GCF_LOCK);
    type = (flags & GCF_TYPEMASK);
    deep = GC_THING_IS_DEEP(type, thing);

    /*
     * Avoid adding a rt->gcLocksHash entry for shallow things until someone
     * nests a lock -- then start such an entry with a count of 2, not 1.
     */
    if (lock || deep) {
        if (!rt->gcLocksHash) {
            rt->gcLocksHash =