| 1 | // Copyright (C) 2024 Jarek Kobus |
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| 2 | // Copyright (C) 2024 The Qt Company Ltd. |
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| 3 | // SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only |
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| 4 | |
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| 5 | #ifndef TASKING_QPROCESSTASK_H |
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| 6 | #define TASKING_QPROCESSTASK_H |
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| 7 | |
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| 8 | // |
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| 9 | // W A R N I N G |
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| 10 | // ------------- |
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| 11 | // |
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| 12 | // This file is not part of the Qt API. It exists purely as an |
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| 13 | // implementation detail. This header file may change from version to |
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| 14 | // version without notice, or even be removed. |
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| 15 | // |
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| 16 | // We mean it. |
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| 17 | // |
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| 18 | |
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| 19 | #include "tasking_global.h" |
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| 20 | |
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| 21 | #include "tasktree.h" |
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| 22 | |
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| 23 | #include <QtCore/QProcess> |
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| 24 | |
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| 25 | QT_BEGIN_NAMESPACE |
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| 26 | |
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| 27 | #if QT_CONFIG(process) |
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| 28 | |
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| 29 | namespace Tasking { |
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| 30 | |
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| 31 | // Deleting a running QProcess may block the caller thread up to 30 seconds and issue warnings. |
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| 32 | // To avoid these issues we move the running QProcess into a separate thread |
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| 33 | // managed by the internal ProcessReaper, instead of deleting it immediately. |
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| 34 | // Inside the ProcessReaper's thread we try to finish the process in a most gentle way: |
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| 35 | // we call QProcess::terminate() with 500 ms timeout, and if the process is still running |
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| 36 | // after this timeout passed, we call QProcess::kill() and wait for the process to finish. |
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| 37 | // All these handlings are done is a separate thread, so the main thread doesn't block at all |
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| 38 | // when the QProcessTask is destructed. |
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| 39 | // Finally, on application quit, QProcessDeleter::deleteAll() should be called in order |
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| 40 | // to synchronize all the processes being still potentially reaped in a separate thread. |
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| 41 | // The call to QProcessDeleter::deleteAll() is blocking in case some processes |
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| 42 | // are still being reaped. |
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| 43 | // This strategy seems most sensible, since when passing the running QProcess into the |
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| 44 | // ProcessReaper we don't block immediately, but postpone the possible (not certain) block |
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| 45 | // until the end of an application. |
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| 46 | // In this way we terminate the running processes in the most safe way and keep the main thread |
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| 47 | // responsive. That's a common case when the running application wants to terminate the QProcess |
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| 48 | // immediately (e.g. on Cancel button pressed), without keeping and managing the handle |
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| 49 | // to the still running QProcess. |
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| 50 | |
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| 51 | // The implementation of the internal reaper is inspired by the Utils::ProcessReaper taken |
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| 52 | // from the QtCreator codebase. |
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| 53 | |
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| 54 | class TASKING_EXPORT QProcessDeleter |
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| 55 | { |
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| 56 | public: |
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| 57 | // Blocking, should be called after all QProcessAdapter instances are deleted. |
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| 58 | static void deleteAll(); |
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| 59 | void operator()(QProcess *process); |
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| 60 | }; |
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| 61 | |
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| 62 | class TASKING_EXPORT QProcessAdapter : public TaskAdapter<QProcess, QProcessDeleter> |
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| 63 | { |
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| 64 | private: |
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| 65 | void start() final { |
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| 66 | connect(sender: task(), signal: &QProcess::finished, context: this, slot: [this] { |
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| 67 | const bool success = task()->exitStatus() == QProcess::NormalExit |
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| 68 | && task()->error() == QProcess::UnknownError |
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| 69 | && task()->exitCode() == 0; |
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| 70 | Q_EMIT done(result: toDoneResult(success)); |
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| 71 | }); |
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| 72 | connect(sender: task(), signal: &QProcess::errorOccurred, context: this, slot: [this](QProcess::ProcessError error) { |
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| 73 | if (error != QProcess::FailedToStart) |
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| 74 | return; |
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| 75 | Q_EMIT done(result: DoneResult::Error); |
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| 76 | }); |
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| 77 | task()->start(); |
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| 78 | } |
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| 79 | }; |
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| 80 | |
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| 81 | using QProcessTask = CustomTask<QProcessAdapter>; |
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| 82 | |
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| 83 | } // namespace Tasking |
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| 84 | |
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| 85 | #endif // QT_CONFIG(process) |
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| 86 | |
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| 87 | QT_END_NAMESPACE |
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| 88 | |
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| 89 | #endif // TASKING_QPROCESSTASK_H |
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| 90 | |
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