Source/WebCore/Modules/webdatabase/DatabaseThread.cpp

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#include "config.h"
#include "DatabaseThread.h"

#if ENABLE(SQL_DATABASE)

#include "Database.h"
#include "DatabaseTask.h"
#include "Logging.h"
#include "SQLTransactionClient.h"
#include "SQLTransactionCoordinator.h"
#include <wtf/AutodrainedPool.h>
#include <wtf/UnusedParam.h>

namespace WebCore {

DatabaseThread::DatabaseThread()
    : m_threadID(0)
    , m_transactionClient(adoptPtr(new SQLTransactionClient()))
    , m_transactionCoordinator(adoptPtr(new SQLTransactionCoordinator()))
    , m_cleanupSync(0)
{
    m_selfRef = this;
}

DatabaseThread::~DatabaseThread()
{
    // The DatabaseThread will only be destructed when both its owner
    // DatabaseContext has deref'ed it, and the databaseThread() thread function
    // has deref'ed the DatabaseThread object. The DatabaseContext destructor
    // will take care of ensuring that a termination request has been issued.
    // The termination request will trigger an orderly shutdown of the thread
    // function databaseThread(). In shutdown, databaseThread() will deref the
    // DatabaseThread before returning.
    ASSERT(terminationRequested());
}

bool DatabaseThread::start()
{
    MutexLocker lock(m_threadCreationMutex);

    if (m_threadID)
        return true;

    m_threadID = createThread(DatabaseThread::databaseThreadStart, this, "WebCore: Database");

    return m_threadID;
}

void DatabaseThread::requestTermination(DatabaseTaskSynchronizer *cleanupSync)
{
    m_cleanupSync = cleanupSync;
    LOG(StorageAPI, "DatabaseThread %p was asked to terminate\n", this);
    m_queue.kill();
}

bool DatabaseThread::terminationRequested(DatabaseTaskSynchronizer* taskSynchronizer) const
{
#ifndef NDEBUG
    if (taskSynchronizer)
        taskSynchronizer->setHasCheckedForTermination();
#else
    UNUSED_PARAM(taskSynchronizer);
#endif

    return m_queue.killed();
}

void DatabaseThread::databaseThreadStart(void* vDatabaseThread)
{
    DatabaseThread* dbThread = static_cast<DatabaseThread*>(vDatabaseThread);
    dbThread->databaseThread();
}

void DatabaseThread::databaseThread()
{
    {
        // Wait for DatabaseThread::start() to complete.
        MutexLocker lock(m_threadCreationMutex);
        LOG(StorageAPI, "Started DatabaseThread %p", this);
    }

    AutodrainedPool pool;
    while (OwnPtr<DatabaseTask> task = m_queue.waitForMessage()) {
        task->performTask();
        pool.cycle();
    }

    // Clean up the list of all pending transactions on this database thread
    m_transactionCoordinator->shutdown();

    LOG(StorageAPI, "About to detach thread %i and clear the ref to DatabaseThread %p, which currently has %i ref(s)", m_threadID, this, refCount());

    // Close the databases that we ran transactions on. This ensures that if any transactions are still open, they are rolled back and we don't leave the database in an
    // inconsistent or locked state.
    if (m_openDatabaseSet.size() > 0) {
        // As the call to close will modify the original set, we must take a copy to iterate over.
        DatabaseSet openSetCopy;
        openSetCopy.swap(m_openDatabaseSet);
        DatabaseSet::iterator end = openSetCopy.end();
        for (DatabaseSet::iterator it = openSetCopy.begin(); it != end; ++it)
            (*it).get()->close();
    }

    // Detach the thread so its resources are no longer of any concern to anyone else
    detachThread(m_threadID);

    DatabaseTaskSynchronizer* cleanupSync = m_cleanupSync;

    // Clear the self refptr, possibly resulting in deletion
    m_selfRef = 0;

    if (cleanupSync) // Someone wanted to know when we were done cleaning up.
        cleanupSync->taskCompleted();
}

void DatabaseThread::recordDatabaseOpen(DatabaseBackend* database)
{
    ASSERT(currentThread() == m_threadID);
    ASSERT(database);
    ASSERT(!m_openDatabaseSet.contains(database));
    m_openDatabaseSet.add(database);
}

void DatabaseThread::recordDatabaseClosed(DatabaseBackend* database)
{
    ASSERT(currentThread() == m_threadID);
    ASSERT(database);
    ASSERT(m_queue.killed() || m_openDatabaseSet.contains(database));
    m_openDatabaseSet.remove(database);
}

void DatabaseThread::scheduleTask(PassOwnPtr<DatabaseTask> task)
{
    ASSERT(!task->hasSynchronizer() || task->hasCheckedForTermination());
    m_queue.append(task);
}

void DatabaseThread::scheduleImmediateTask(PassOwnPtr<DatabaseTask> task)
{
    ASSERT(!task->hasSynchronizer() || task->hasCheckedForTermination());
    m_queue.prepend(task);
}

class SameDatabasePredicate {
public:
    SameDatabasePredicate(const DatabaseBackend* database) : m_database(database) { }
    bool operator()(DatabaseTask* task) const { return task->database() == m_database; }
private:
    const DatabaseBackend* m_database;
};

void DatabaseThread::unscheduleDatabaseTasks(DatabaseBackend* database)
{
    // Note that the thread loop is running, so some tasks for the database
    // may still be executed. This is unavoidable.
    SameDatabasePredicate predicate(database);
    m_queue.removeIf(predicate);
}
} // namespace WebCore
#endif