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Fix potential race conditions and crashes during shutdown #2525

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uklotzde wants to merge 2 commits into from
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Fix potential race conditions and crashes during shutdown #2525

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948ddec
Fix potential race conditions and crashes during shutdown
uklotzde Feb 29, 2020
ede8b69
Explain rationale behind constant
uklotzde Feb 29, 2020
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23 changes: 23 additions & 0 deletions src/library/trackcollectionmanager.cpp
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
#include "library/trackcollectionmanager.h"

#include <QThreadPool>

#include "library/externaltrackcollection.h"
#include "library/scanner/libraryscanner.h"
#include "library/trackcollection.h"
Expand All @@ -17,6 +19,11 @@ const QString kConfigGroup = QStringLiteral("[TrackCollection]");

const ConfigKey kConfigKeyRepairDatabaseOnNextRestart(kConfigGroup, "RepairDatabaseOnNextRestart");

// Prevent infinite delays during shutdown. Long enough to finish
// the pending tasks and short enough to prevent users from killing
// the process.
constexpr int kThreadPoolTimeoutMillisOnShutdown = 30000; // 30 sec
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inline
parented_ptr<TrackCollection> createInternalTrackCollection(
TrackCollectionManager* parent,
Expand Down Expand Up @@ -136,9 +143,23 @@ TrackCollectionManager::~TrackCollectionManager() {
kLogger.warning() << "BaseTrackCache is still in use";
}

// Ensure that all pending, concurrent tasks have been either
// cancelled or finished to prevent access to tracks in
// GlobalTrackCache before it gets deactivated.
kLogger.info()
<< "Stopping all pending tasks in worker threads";
QThreadPool::globalInstance()->clear();
if (!QThreadPool::globalInstance()->waitForDone(
kThreadPoolTimeoutMillisOnShutdown)) {
kLogger.warning()
<< "Failed to stop pending tasks in worker threads";
}

// Evict all remaining tracks from the cache to trigger
// updating of modified tracks. We assume that no other
// components are accessing those files at this point.
kLogger.info()
<< "Deactivating global track cache";
GlobalTrackCacheLocker().deactivateCache();

for (const auto& externalCollection : m_externalCollections) {
Expand All @@ -153,6 +174,8 @@ TrackCollectionManager::~TrackCollectionManager() {

m_pInternalCollection->disconnectDatabase();

kLogger.info()
<< "Destroying global track cache";
GlobalTrackCache::destroyInstance();
}

Expand Down