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QetLogger (discussion #644, steps 1-3) captures whatever an explicit qDebug()/qInfo()/qWarning() call already decided to report. Most of a session -- painting, dragging, a slow synchronous operation -- produces no log output at all, so a silent multi-second gap in the log is indistinguishable from the user simply not doing anything. That gap came up directly: investigating a user-reported "the program lagged" required inferring stalls from timestamp gaps between unrelated log lines, which can't tell a real freeze apart from normal idle time. EventLoopWatchdog closes that gap directly instead of inferring it. A QTimer::PreciseTimer repeating tick (every 50ms) measures the *actual* elapsed time since the previous tick via QElapsedTimer (monotonic, unaffected by system clock/NTP adjustments). Qt does not queue up missed fires for a normal repeating timer, so if the main thread is blocked for 600ms, the timer fires once as soon as the loop frees up, with ~600ms measured since the last tick -- that gap is the stall, measured at its source. Only logs (via the existing qWarning() path, so it reuses QetLogger's file/ring/rotation with no new plumbing) when a tick is late by more than 200ms, so a healthy session produces zero output from this class, in keeping with QetLogger's bounded-log design. Same QET_WATCHDOG_DISABLE=1 escape-hatch convention as QetLogger's own QET_LOG_DISABLE=1. Deliberately not included: attributing a stall to what caused it. This tells you a stall happened and how long -- pairing that timestamp with gdb attached to a running session (as used for the CLI hang, PR #661) is still how you get from "it stalled" to a root cause. Stacked on #647 (feature-diagnostic-logging-crash) for QetLogger/ qWarning() plumbing this depends on -- diff includes its commits until that merges. Verified against the compiled binary, not just read: temporarily injected a QThread::msleep(600) via a one-shot QTimer 2s after startup, confirmed the exact expected warning ("EventLoopWatchdog: main thread stalled for 620 ms") at the right severity through the real qWarning()/QetLogger path, then removed the test hook and reconfirmed a normal run produces no output from this class at all.
59 lines
1.9 KiB
C++
59 lines
1.9 KiB
C++
/*
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Copyright 2006-2026 The QElectroTech Team
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This file is part of QElectroTech.
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QElectroTech is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 2 of the License, or
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(at your option) any later version.
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QElectroTech is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with QElectroTech. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "eventloopwatchdog.h"
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#include <QDebug>
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#include <QProcessEnvironment>
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EventLoopWatchdog::EventLoopWatchdog(QObject *parent) :
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QObject(parent)
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{
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m_disabled = QProcessEnvironment::systemEnvironment()
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.value(QStringLiteral("QET_WATCHDOG_DISABLE")) == QStringLiteral("1");
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// Precise, not the default Coarse: Coarse explicitly trades timing
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// accuracy for power/scheduling efficiency (platform-dependent, but
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// commonly +/- a double-digit percentage), which would show up as
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// noise indistinguishable from a real stall in exactly the
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// measurement this class exists to make trustworthy.
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m_timer.setTimerType(Qt::PreciseTimer);
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connect(&m_timer, &QTimer::timeout, this, &EventLoopWatchdog::tick);
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}
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void EventLoopWatchdog::start()
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{
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if (m_disabled)
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return;
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m_elapsed.start();
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m_timer.start(kTickIntervalMs);
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}
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void EventLoopWatchdog::tick()
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{
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// restart() returns the elapsed time and resets the clock in one
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// call, so this tick's own cost is never counted against the next.
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const qint64 actual_ms = m_elapsed.restart();
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if (actual_ms > kStallThresholdMs) {
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qWarning() << "EventLoopWatchdog: main thread stalled for"
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<< actual_ms << "ms (expected a tick every"
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<< kTickIntervalMs << "ms)";
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}
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}
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