EventLoop.cc

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/*
 * Copyright (C) 1996-2025 The Squid Software Foundation and contributors
 *
 * Squid software is distributed under GPLv2+ license and includes
 * contributions from numerous individuals and organizations.
 * Please see the COPYING and CONTRIBUTORS files for details.
 */
 
/* DEBUG: section 01    Main Loop */
 
#include "squid.h"
#include "AsyncEngine.h"
#include "base/AsyncCallQueue.h"
#include "debug/Stream.h"
#include "EventLoop.h"
#include "fatal.h"
#include "time/Engine.h"
 
EventLoop *EventLoop::Running = nullptr;
 
EventLoop::EventLoop() : errcount(0), last_loop(false), timeService(nullptr),
    primaryEngine(nullptr),
    loop_delay(EVENT_LOOP_TIMEOUT),
    error(false),
    runOnceResult(false)
{}
 
void
EventLoop::checkEngine(AsyncEngine * engine, bool const primary)
{
    int requested_delay;
 
    if (!primary)
        requested_delay = engine->checkEvents(0);
    else
        requested_delay = engine->checkEvents(loop_delay);
 
    if (requested_delay < 0)
        switch (requested_delay) {
 
        case AsyncEngine::EVENT_IDLE:
            debugs(1, 9, "Engine " << engine << " is idle.");
            break;
 
        case AsyncEngine::EVENT_ERROR:
            runOnceResult = false;
            error = true;
            break;
 
        default:
            fatal_dump("unknown AsyncEngine result");
        }
    else {
        /* not idle or error */
        runOnceResult = false;
 
        if (requested_delay < loop_delay)
            loop_delay = requested_delay;
    }
}
 
void
EventLoop::prepareToRun()
{
    last_loop = false;
    errcount = 0;
}
 
void
EventLoop::registerEngine(AsyncEngine *engine)
{
    engines.push_back(engine);
}
 
void
EventLoop::run()
{
    prepareToRun();
 
    assert(!Running);
    Running = this;
 
    while (!runOnce());
 
    Running = nullptr;
}
 
bool
EventLoop::runOnce()
{
    bool sawActivity = false;
    runOnceResult = true;
    error = false;
    loop_delay = EVENT_LOOP_TIMEOUT;
 
    AsyncEngine *waitingEngine = primaryEngine;
    if (!waitingEngine && !engines.empty())
        waitingEngine = engines.back();
 
    do {
        // generate calls and events
        typedef engine_vector::iterator EVI;
        for (EVI i = engines.begin(); i != engines.end(); ++i) {
            if (*i != waitingEngine)
                checkEngine(*i, false);
        }
 
        // dispatch calls accumulated so far
        sawActivity = dispatchCalls();
        if (sawActivity)
            runOnceResult = false;
    } while (sawActivity);
 
    if (waitingEngine != nullptr)
        checkEngine(waitingEngine, true);
 
    if (timeService != nullptr)
        timeService->tick();
 
    // dispatch calls scheduled by waitingEngine and timeService
    sawActivity = dispatchCalls();
    if (sawActivity)
        runOnceResult = false;
 
    if (error) {
        ++errcount;
        debugs(1, DBG_CRITICAL, "ERROR: Select loop Error. Retry " << errcount);
    } else
        errcount = 0;
 
    if (errcount == 10)
        return true;
 
    if (last_loop)
        return true;
 
    return runOnceResult;
}
 
// dispatches calls accumulated during checkEngine()
bool
EventLoop::dispatchCalls()
{
    bool dispatchedSome = AsyncCallQueue::Instance().fire();
    return dispatchedSome;
}
 
void
EventLoop::setPrimaryEngine(AsyncEngine * engine)
{
    for (engine_vector::iterator i = engines.begin();
            i != engines.end(); ++i)
        if (*i == engine) {
            primaryEngine = engine;
            return;
        }
 
    fatal("EventLoop::setPrimaryEngine: No such engine!.");
}
 
void
EventLoop::setTimeService(Time::Engine *engine)
{
    timeService = engine;
}
 
void
EventLoop::stop()
{
    last_loop = true;
}