C++ dvmUnlockMutex函数代码示例

/*
 * Visits roots.  TODO: visit cached global references.
 */
void dvmVisitRoots(RootVisitor *visitor, void *arg)
{
    assert(visitor != NULL);
    //u4 t0 = dvmGetRelativeTimeMsec();

#ifndef FASTIVA_PRELOAD_STATIC_INSTANCE
    visitHashTable(visitor, gDvm.loadedClasses, ROOT_STICKY_CLASS, arg);
    visitPrimitiveTypes(visitor, arg);
#endif
    if (gDvm.dbgRegistry != NULL) {
        visitHashTable(visitor, gDvm.dbgRegistry, ROOT_DEBUGGER, arg);
    }
    if (gDvm.literalStrings != NULL) {
        visitHashTable(visitor, gDvm.literalStrings, ROOT_INTERNED_STRING, arg);
    }
    dvmLockMutex(&gDvm.jniGlobalRefLock);
    visitIndirectRefTable(visitor, &gDvm.jniGlobalRefTable, 0, ROOT_JNI_GLOBAL, arg);
    dvmUnlockMutex(&gDvm.jniGlobalRefLock);
    dvmLockMutex(&gDvm.jniPinRefLock);
    visitReferenceTable(visitor, &gDvm.jniPinRefTable, 0, ROOT_VM_INTERNAL, arg);
    dvmUnlockMutex(&gDvm.jniPinRefLock);
    visitThreads(visitor, arg);
    (*visitor)(&gDvm.outOfMemoryObj, 0, ROOT_VM_INTERNAL, arg);
    (*visitor)(&gDvm.internalErrorObj, 0, ROOT_VM_INTERNAL, arg);
    (*visitor)(&gDvm.noClassDefFoundErrorObj, 0, ROOT_VM_INTERNAL, arg);
#ifdef FASTIVA
	(*visitor)(&kernelData.g_pAnnotationsList, 0, ROOT_VM_INTERNAL, arg);
#endif
}

/*
 * Crank up the heap worker thread.
 *
 * Does not return until the thread is ready for business.
 */
bool dvmHeapWorkerStartup(void)
{
    assert(!gDvm.haltHeapWorker);
    assert(!gDvm.heapWorkerReady);
    assert(gDvm.heapWorkerHandle == 0);
    assert(gDvm.heapWorkerInitialized);

    /* use heapWorkerLock/heapWorkerCond to communicate readiness */
    dvmLockMutex(&gDvm.heapWorkerLock);

//BUG: If a GC happens in here or in the new thread while we hold the lock,
//     the GC will deadlock when trying to acquire heapWorkerLock.
    if (!dvmCreateInternalThread(&gDvm.heapWorkerHandle,
                "HeapWorker", heapWorkerThreadStart, NULL))
    {
        dvmUnlockMutex(&gDvm.heapWorkerLock);
        return false;
    }

    /*
     * Wait for the heap worker to come up.  We know the thread was created,
     * so this should not get stuck.
     */
    while (!gDvm.heapWorkerReady) {
        dvmWaitCond(&gDvm.heapWorkerCond, &gDvm.heapWorkerLock);
    }

    dvmUnlockMutex(&gDvm.heapWorkerLock);
    return true;
}

/*
 * Implement java.lang.Thread.interrupt().
 */
void dvmThreadInterrupt(Thread* thread)
{
    assert(thread != NULL);

    dvmLockMutex(&thread->waitMutex);

    /*
     * If the interrupted flag is already set no additional action is
     * required.
     */
    if (thread->interrupted == true) {
        dvmUnlockMutex(&thread->waitMutex);
        return;
    }

    /*
     * Raise the "interrupted" flag.  This will cause it to bail early out
     * of the next wait() attempt, if it's not currently waiting on
     * something.
     */
    thread->interrupted = true;

    /*
     * Is the thread waiting?
     *
     * Note that fat vs. thin doesn't matter here;  waitMonitor
     * is only set when a thread actually waits on a monitor,
     * which implies that the monitor has already been fattened.
     */
    if (thread->waitMonitor != NULL) {
        pthread_cond_signal(&thread->waitCond);
    }

    dvmUnlockMutex(&thread->waitMutex);
}

/*
 * Notify one thread waiting on this monitor.
 */
static void notifyMonitor(Thread* self, Monitor* mon)
{
    Thread* thread;

    assert(self != NULL);
    assert(mon != NULL);

    /* Make sure that we hold the lock. */
    if (mon->owner != self) {
        dvmThrowIllegalMonitorStateException(
            "object not locked by thread before notify()");
        return;
    }
    /* Signal the first waiting thread in the wait set. */
    while (mon->waitSet != NULL) {
        thread = mon->waitSet;
        mon->waitSet = thread->waitNext;
        thread->waitNext = NULL;
        dvmLockMutex(&thread->waitMutex);
        /* Check to see if the thread is still waiting. */
        if (thread->waitMonitor != NULL) {
            pthread_cond_signal(&thread->waitCond);
            dvmUnlockMutex(&thread->waitMutex);
            return;
        }
        dvmUnlockMutex(&thread->waitMutex);
    }
}

void dvmCompilerUpdateGlobalState()
{
    bool jitActive;
    bool jitActivate;
    bool needUnchain = false;

    /*
     * The tableLock might not be initialized yet by the compiler thread if
     * debugger is attached from the very beginning of the VM launch. If
     * pProfTableCopy is NULL, the lock is not initialized yet and we don't
     * need to refresh anything either.
     */
    if (gDvmJit.pProfTableCopy == NULL) {
        return;
    }

    /*
     * On the first enabling of method tracing, switch the compiler
     * into a mode that includes trace support for invokes and returns.
     * If there are any existing translations, flush them.  NOTE:  we
     * can't blindly flush the translation cache because this code
     * may be executed before the compiler thread has finished
     * initialization.
     */
    if ((gDvm.activeProfilers != 0) &&
        !gDvmJit.methodTraceSupport) {
        bool resetRequired;
        /*
         * compilerLock will prevent new compilations from being
         * installed while we are working.
         */
        dvmLockMutex(&gDvmJit.compilerLock);
        gDvmJit.cacheVersion++; // invalidate compilations in flight
        gDvmJit.methodTraceSupport = true;
        resetRequired = (gDvmJit.numCompilations != 0);
        dvmUnlockMutex(&gDvmJit.compilerLock);
        if (resetRequired) {
            dvmSuspendAllThreads(SUSPEND_FOR_CC_RESET);
            resetCodeCache();
            dvmResumeAllThreads(SUSPEND_FOR_CC_RESET);
        }
    }

    dvmLockMutex(&gDvmJit.tableLock);
    jitActive = gDvmJit.pProfTable != NULL;
    jitActivate = !dvmDebuggerOrProfilerActive();

    if (jitActivate && !jitActive) {
        gDvmJit.pProfTable = gDvmJit.pProfTableCopy;
    } else if (!jitActivate && jitActive) {
        gDvmJit.pProfTable = NULL;
        needUnchain = true;
    }
    dvmUnlockMutex(&gDvmJit.tableLock);
    if (needUnchain)
        dvmJitUnchainAll();
    // Make sure all threads have current values
    dvmJitUpdateThreadStateAll();
}

/*
 * Attempt to enqueue a work order, returning true if successful.
 *
 * NOTE: Make sure that the caller frees the info pointer if the return value
 * is false.
 */
bool dvmCompilerWorkEnqueue(const u2 *pc, WorkOrderKind kind, void* info)
{
    int cc;
    int i;
    int numWork;
    bool result = true;

    dvmLockMutex(&gDvmJit.compilerLock);

    /*
     * Return if queue or code cache is full.
     */
    if (gDvmJit.compilerQueueLength == COMPILER_WORK_QUEUE_SIZE ||
        gDvmJit.codeCacheFull == true) {
        dvmUnlockMutex(&gDvmJit.compilerLock);
        return false;
    }

    for (numWork = gDvmJit.compilerQueueLength,
           i = gDvmJit.compilerWorkDequeueIndex;
         numWork > 0;
         numWork--) {
        /* Already enqueued */
        if (gDvmJit.compilerWorkQueue[i++].pc == pc) {
            dvmUnlockMutex(&gDvmJit.compilerLock);
            return true;
        }
        /* Wrap around */
        if (i == COMPILER_WORK_QUEUE_SIZE)
            i = 0;
    }

    CompilerWorkOrder *newOrder =
        &gDvmJit.compilerWorkQueue[gDvmJit.compilerWorkEnqueueIndex];
    newOrder->pc = pc;
    newOrder->kind = kind;
    newOrder->info = info;
    newOrder->result.methodCompilationAborted = false;
    newOrder->result.codeAddress = NULL;
    newOrder->result.discardResult =
        (kind == kWorkOrderTraceDebug) ? true : false;
    newOrder->result.cacheVersion = gDvmJit.cacheVersion;
    newOrder->result.requestingThread = dvmThreadSelf();

    gDvmJit.compilerWorkEnqueueIndex++;
    if (gDvmJit.compilerWorkEnqueueIndex == COMPILER_WORK_QUEUE_SIZE)
        gDvmJit.compilerWorkEnqueueIndex = 0;
    gDvmJit.compilerQueueLength++;
    cc = pthread_cond_signal(&gDvmJit.compilerQueueActivity);
    assert(cc == 0);

    dvmUnlockMutex(&gDvmJit.compilerLock);
    return result;
}

/**
 * Jit编译器入口点函数
 * @retval 0 表示失败
 * @retval 1 表示成功 
 */
bool dvmCompilerStartup(void)
{
	/* 初始化一些线程同步方面的变量 */
    dvmInitMutex(&gDvmJit.compilerLock);
    dvmInitMutex(&gDvmJit.compilerICPatchLock);
    dvmInitMutex(&gDvmJit.codeCacheProtectionLock);
    dvmLockMutex(&gDvmJit.compilerLock);
    pthread_cond_init(&gDvmJit.compilerQueueActivity, NULL);
    pthread_cond_init(&gDvmJit.compilerQueueEmpty, NULL);

    /* Reset the work queue */
	/* 设置工作队列 */
    gDvmJit.compilerWorkEnqueueIndex = gDvmJit.compilerWorkDequeueIndex = 0;
    gDvmJit.compilerQueueLength = 0;
    dvmUnlockMutex(&gDvmJit.compilerLock);

    /*
     * Defer rest of initialization until we're sure JIT'ng makes sense. Launch
     * the compiler thread, which will do the real initialization if and
     * when it is signalled to do so.
     */
	/*
	 * 以下这个函数创建compilerThreadStart编译线程，当这条线程会执行真正的初始化工作
	 */
    return dvmCreateInternalThread(&gDvmJit.compilerHandle, "Compiler",
                                   compilerThreadStart, NULL);
}

/*
 * For debugging, dump the contents of a linear alloc area.
 *
 * We grab the lock so that the header contents and list output are
 * consistent.
 */
void dvmLinearAllocDump(Object* classLoader)
{
#ifdef DISABLE_LINEAR_ALLOC
    return;
#endif
    LinearAllocHdr* pHdr = getHeader(classLoader);

    dvmLockMutex(&pHdr->lock);

    LOGI("LinearAlloc classLoader=%p\n", classLoader);
    LOGI("  mapAddr=%p mapLength=%d firstOffset=%d\n",
        pHdr->mapAddr, pHdr->mapLength, pHdr->firstOffset);
    LOGI("  curOffset=%d\n", pHdr->curOffset);

    int off = pHdr->firstOffset;
    u4 rawLen, fullLen;

    while (off < pHdr->curOffset) {
        rawLen = *(u4*) (pHdr->mapAddr + off);
        fullLen = ((HEADER_EXTRA*2 + (rawLen & LENGTHFLAG_MASK))
                    & ~(BLOCK_ALIGN-1));

        LOGI("  %p (%3d): %clen=%d%s\n", pHdr->mapAddr + off + HEADER_EXTRA,
            (int) ((off + HEADER_EXTRA) / PAGESIZE),
            (rawLen & LENGTHFLAG_FREE) != 0 ? '*' : ' ',
            rawLen & LENGTHFLAG_MASK,
            (rawLen & LENGTHFLAG_RW) != 0 ? " [RW]" : "");

        off += fullLen;
    }

    if (ENFORCE_READ_ONLY) {
        LOGI("writeRefCount map:\n");

        int numPages = (pHdr->mapLength+PAGESIZE-1) / PAGESIZE;
        int zstart = 0;
        int i;

        for (i = 0; i < numPages; i++) {
            int count = pHdr->writeRefCount[i];

            if (count != 0) {
                if (zstart < i-1)
                    printf(" %d-%d: zero\n", zstart, i-1);
                else if (zstart == i-1)
                    printf(" %d: zero\n", zstart);
                zstart = i+1;
                printf(" %d: %d\n", i, count);
            }
        }
        if (zstart < i)
            printf(" %d-%d: zero\n", zstart, i-1);
    }

    LOGD("LinearAlloc %p using %d of %d (%d%%)\n",
        classLoader, pHdr->curOffset, pHdr->mapLength,
        (pHdr->curOffset * 100) / pHdr->mapLength);

    dvmUnlockMutex(&pHdr->lock);
}

/*
 * Unlock a monitor.
 *
 * Returns true if the unlock succeeded.
 * If the unlock failed, an exception will be pending.
 */
static bool unlockMonitor(Thread* self, Monitor* mon)
{
    assert(self != NULL);
    assert(mon != NULL);
    if (mon->owner == self) {
        /*
         * We own the monitor, so nobody else can be in here.
         */
        if (mon->lockCount == 0) {
            mon->owner = NULL;
            mon->ownerMethod = NULL;
            mon->ownerPc = 0;
            dvmUnlockMutex(&mon->lock);
        } else {
            mon->lockCount--;
        }
    } else {
        /*
         * We don't own this, so we're not allowed to unlock it.
         * The JNI spec says that we should throw IllegalMonitorStateException
         * in this case.
         */
        dvmThrowIllegalMonitorStateException("unlock of unowned monitor");
        return false;
    }
    return true;
}

/*
 * Verify that all blocks are freed.
 *
 * This should only be done as we're shutting down, but there could be a
 * daemon thread that's still trying to do something, so we grab the locks.
 */
static void checkAllFree(Object* classLoader)
{
#ifdef DISABLE_LINEAR_ALLOC
    return;
#endif
    LinearAllocHdr* pHdr = getHeader(classLoader);

    dvmLockMutex(&pHdr->lock);

    int off = pHdr->firstOffset;
    u4 rawLen, fullLen;

    while (off < pHdr->curOffset) {
        rawLen = *(u4*) (pHdr->mapAddr + off);
        fullLen = ((HEADER_EXTRA*2 + (rawLen & LENGTHFLAG_MASK))
                    & ~(BLOCK_ALIGN-1));

        if ((rawLen & LENGTHFLAG_FREE) == 0) {
            LOGW("LinearAlloc %p not freed: %p len=%d\n", classLoader,
                pHdr->mapAddr + off + HEADER_EXTRA, rawLen & LENGTHFLAG_MASK);
        }

        off += fullLen;
    }

    dvmUnlockMutex(&pHdr->lock);
}

/*
Change the 2-byte value at the specified address to a new value.  If the
location already has the new value, do nothing.

Otherwise works like dvmDexChangeDex1.

在指定位置改变一个双字节值为新值。如果该位置已经有新值，不作任何事情。

否则处理类似dvmDexChangeDex1。
*/
bool dvmDexChangeDex2(DvmDex* pDvmDex, u2* addr, u2 newVal)
{
    if (*addr == newVal) {
        ALOGV("+++ value at %p is already 0x%04x", addr, newVal);
        return true;
    }

    /*
     * We're not holding this for long, so we don't bother with switching
     * to VMWAIT.
     */
    dvmLockMutex(&pDvmDex->modLock);

    ALOGV("+++ change 2byte at %p from 0x%04x to 0x%04x", addr, *addr, newVal);
    if (sysChangeMapAccess(addr, 2, true, &pDvmDex->memMap) != 0) {
        ALOGD("NOTE: DEX page access change (->RW) failed");
        /* expected on files mounted from FAT; keep going (may crash) */
    }

    *addr = newVal;

    if (sysChangeMapAccess(addr, 2, false, &pDvmDex->memMap) != 0) {
        ALOGD("NOTE: DEX page access change (->RO) failed");
        /* expected on files mounted from FAT; keep going */
    }

    dvmUnlockMutex(&pDvmDex->modLock);

    return true;
}

static StringObject* lookupInternedString(StringObject* strObj, bool isLiteral)
{
    StringObject* found;

    assert(strObj != NULL);
    u4 key = dvmComputeStringHash(strObj);
    dvmLockMutex(&gDvm.internLock);
    if (isLiteral) {
        /*
         * Check the literal table for a match.
         */
        StringObject* literal = lookupString(gDvm.literalStrings, key, strObj);
        if (literal != NULL) {
            /*
             * A match was found in the literal table, the easy case.
             */
            found = literal;
        } else {
            /*
             * There is no match in the literal table, check the
             * interned string table.
             */
            StringObject* interned = lookupString(gDvm.internedStrings, key, strObj);
            if (interned != NULL) {
                /*
                 * A match was found in the interned table.  Move the
                 * matching string to the literal table.
                 */
                dvmHashTableRemove(gDvm.internedStrings, key, interned);
                found = insertString(gDvm.literalStrings, key, interned);
                assert(found == interned);
            } else {
                /*
                 * No match in the literal table or the interned
                 * table.  Insert into the literal table.
                 */
                found = insertString(gDvm.literalStrings, key, strObj);
                assert(found == strObj);
            }
        }
    } else {
        /*
         * Check the literal table for a match.
         */
        found = lookupString(gDvm.literalStrings, key, strObj);
        if (found == NULL) {
            /*
             * No match was found in the literal table.  Insert into
             * the intern table if it does not already exist.
             */
            found = insertString(gDvm.internedStrings, key, strObj);
        }
    }
    assert(found != NULL);
    dvmUnlockMutex(&gDvm.internLock);
    return found;
}

static void gcDaemonShutdown()
{
    if (gHs->hasGcThread) {
        dvmLockMutex(&gHs->gcThreadMutex);
        gHs->gcThreadShutdown = true;
        dvmSignalCond(&gHs->gcThreadCond);
        dvmUnlockMutex(&gHs->gcThreadMutex);
        pthread_join(gHs->gcThread, NULL);
    }
}

/*
 * Clear white references from the intern table.
 */
void dvmGcDetachDeadInternedStrings(int (*isUnmarkedObject)(void *))
{
    /* It's possible for a GC to happen before dvmStringInternStartup()
     * is called.
     */
    if (gDvm.internedStrings != NULL) {
        dvmLockMutex(&gDvm.internLock);
        dvmHashForeachRemove(gDvm.internedStrings, isUnmarkedObject);
        dvmUnlockMutex(&gDvm.internLock);
    }
}

/*
 * Returns true if the object is a weak interned string.  Any string
 * interned by the user is weak.
 */
bool dvmIsWeakInternedString(StringObject* strObj)
{
    assert(strObj != NULL);
    if (gDvm.internedStrings == NULL) {
        return false;
    }
    dvmLockMutex(&gDvm.internLock);
    u4 key = dvmComputeStringHash(strObj);
    StringObject* found = lookupString(gDvm.internedStrings, key, strObj);
    dvmUnlockMutex(&gDvm.internLock);
    return found == strObj;
}