From 23047f16f7c8f4b0fe9a05e9738207e519858573 Mon Sep 17 00:00:00 2001
From: Jarek Kobus <jaroslaw.kobus@qt.io>
Date: Mon, 15 Feb 2021 10:47:21 +0100
Subject: [PATCH] ClassView: Get rid of project and document mutexes

In fact, all the methods inside Parser class are
called only in one thread (parser thread), which runs
his own event loop. The exception is 3 methods
(canFetchMore(), fetchMore() and hasChildren()),
which may be called concurrently from the main thread.
However, they are protected with another mutex.
So, project and document mutex were protecting
the access to internals only when called from
one, always the same thread, what is not needed at all.

Task-number: QTCREATORBUG-25317
Change-Id: I0b44b762b5d76d003035e9c3099c90568b7faf80
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>
---
 src/plugins/classview/classviewparser.cpp | 35 ++++++-----------------
 1 file changed, 8 insertions(+), 27 deletions(-)

diff --git a/src/plugins/classview/classviewparser.cpp b/src/plugins/classview/classviewparser.cpp
index b56baba0724..2dea77edc97 100644
--- a/src/plugins/classview/classviewparser.cpp
+++ b/src/plugins/classview/classviewparser.cpp
@@ -97,9 +97,6 @@ public:
 
     QTimer timer;
 
-    QReadWriteLock m_documentLock;
-    QReadWriteLock m_projectLock;
-
     struct DocumentCache {
         unsigned treeRevision = 0;
         ParserTreeItem::Ptr tree;
@@ -383,7 +380,6 @@ ParserTreeItem::Ptr Parser::getParseProjectTree(const QStringList &fileList,
     ParserTreeItem::Ptr item(new ParserTreeItem());
     unsigned revision = 0;
     foreach (const QString &file, fileList) {
-        // ? locker for document?..
         const CPlusPlus::Document::Ptr &doc = d->document(file);
         if (doc.isNull())
             continue;
@@ -400,8 +396,6 @@ ParserTreeItem::Ptr Parser::getParseProjectTree(const QStringList &fileList,
 
     // update the cache
     if (!projectId.isEmpty()) {
-        QWriteLocker locker(&d->m_projectLock);
-
         ParserPrivate::ProjectCache &projectCache = d->m_projectCache[projectId];
         projectCache.tree = item;
         projectCache.treeRevision = revision;
@@ -418,8 +412,6 @@ ParserTreeItem::Ptr Parser::getParseProjectTree(const QStringList &fileList,
 ParserTreeItem::Ptr Parser::getCachedOrParseProjectTree(const QStringList &fileList,
                                                 const QString &projectId)
 {
-    QReadLocker locker(&d->m_projectLock);
-
     const auto it = d->m_projectCache.constFind(projectId);
     if (it != d->m_projectCache.constEnd() && !it.value().tree.isNull()) {
         // calculate project's revision
@@ -436,7 +428,6 @@ ParserTreeItem::Ptr Parser::getCachedOrParseProjectTree(const QStringList &fileL
             return it.value().tree;
     }
 
-    locker.unlock();
     return getParseProjectTree(fileList, projectId);
 }
 
@@ -462,7 +453,6 @@ ParserTreeItem::ConstPtr Parser::getParseDocumentTree(const CPlusPlus::Document:
     for (unsigned i = 0; i < total; ++i)
         addSymbol(itemPtr, doc->globalSymbolAt(i));
 
-    QWriteLocker locker(&d->m_documentLock);
     d->m_documentCache.insert(fileName, { doc->revision(), itemPtr, doc } );
     return itemPtr;
 }
@@ -480,13 +470,10 @@ ParserTreeItem::ConstPtr Parser::getCachedOrParseDocumentTree(const CPlusPlus::D
         return ParserTreeItem::ConstPtr();
 
     const QString &fileName = doc->fileName();
-    {
-        QReadLocker locker(&d->m_documentLock);
-        const auto it = d->m_documentCache.constFind(fileName);
-        if (it != d->m_documentCache.constEnd() && !it.value().tree.isNull()
-                && it.value().treeRevision == doc->revision()) {
-            return it.value().tree;
-        }
+    const auto it = d->m_documentCache.constFind(fileName);
+    if (it != d->m_documentCache.constEnd() && !it.value().tree.isNull()
+            && it.value().treeRevision == doc->revision()) {
+        return it.value().tree;
     }
     return getParseDocumentTree(doc);
 }
@@ -533,8 +520,6 @@ void Parser::removeFiles(const QStringList &fileList)
     if (fileList.isEmpty())
         return;
 
-    QWriteLocker projectLocker(&d->m_projectLock);
-    QWriteLocker documentLocker(&d->m_documentLock);
     for (const QString &name : fileList) {
         d->fileList.remove(name);
         d->m_documentCache.remove(name);
@@ -549,14 +534,10 @@ void Parser::removeFiles(const QStringList &fileList)
 */
 void Parser::resetData(const CPlusPlus::Snapshot &snapshot)
 {
-    {
-        QWriteLocker projectLocker(&d->m_projectLock);
-        QWriteLocker documentLocker(&d->m_documentLock);
-        d->m_projectCache.clear();
-        d->m_documentCache.clear();
-        for (auto it = snapshot.begin(); it != snapshot.end(); ++it)
-            d->m_documentCache[it.key().toString()].document = it.value();
-    }
+    d->m_projectCache.clear();
+    d->m_documentCache.clear();
+    for (auto it = snapshot.begin(); it != snapshot.end(); ++it)
+        d->m_documentCache[it.key().toString()].document = it.value();
 
     // recalculate file list
     FilePaths fileList;