Remove unnecessary QMutexes in QFileSystemWatcher implementations

The polling, inotify, and kqueue implementations are no longer threaded,
and as such, do not need mutexes to protect their internal data (since
QFileSystemWatcher itself is not documented as a thread-safe API).

The Windows implementation is unchanged as it uses multiple threads
explicitly.

Change-Id: Ia82510397e576bf704ce3aed3d776b58b39f7ff3
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: João Abecasis <joao.abecasis@nokia.com>

7 files changed, 69 insertions, 90 deletions

diff --git a/src/corelib/io/qfilesystemwatcher.cpp b/src/corelib/io/qfilesystemwatcher.cpp
index 85b27c9ec9..b6eb5eda5a 100644
--- a/src/corelib/io/qfilesystemwatcher.cpp
+++ b/src/corelib/io/qfilesystemwatcher.cpp
@@ -48,7 +48,6 @@
 #include <qdebug.h>
 #include <qdir.h>
 #include <qfileinfo.h>
-#include <qmutex.h>
 #include <qset.h>
 #include <qtimer.h>
 
diff --git a/src/corelib/io/qfilesystemwatcher_inotify.cpp b/src/corelib/io/qfilesystemwatcher_inotify.cpp
index 80eb6303cc..49299e2254 100644
--- a/src/corelib/io/qfilesystemwatcher_inotify.cpp
+++ b/src/corelib/io/qfilesystemwatcher_inotify.cpp
@@ -245,8 +245,6 @@ QStringList QInotifyFileSystemWatcherEngine::addPaths(const QStringList &paths,
                                                       QStringList *files,
                                                       QStringList *directories)
 {
-    QMutexLocker locker(&mutex);
-
     QStringList p = paths;
     QMutableListIterator<QString> it(p);
     while (it.hasNext()) {
@@ -303,8 +301,6 @@ QStringList QInotifyFileSystemWatcherEngine::removePaths(const QStringList &path
                                                          QStringList *files,
                                                          QStringList *directories)
 {
-    QMutexLocker locker(&mutex);
-
     QStringList p = paths;
     QMutableListIterator<QString> it(p);
     while (it.hasNext()) {
@@ -331,8 +327,6 @@ QStringList QInotifyFileSystemWatcherEngine::removePaths(const QStringList &path
 
 void QInotifyFileSystemWatcherEngine::readFromInotify()
 {
-    QMutexLocker locker(&mutex);
-
     // qDebug() << "QInotifyFileSystemWatcherEngine::readFromInotify";
 
     int buffSize = 0;
diff --git a/src/corelib/io/qfilesystemwatcher_inotify_p.h b/src/corelib/io/qfilesystemwatcher_inotify_p.h
index 24fc88ffeb..daedb01fac 100644
--- a/src/corelib/io/qfilesystemwatcher_inotify_p.h
+++ b/src/corelib/io/qfilesystemwatcher_inotify_p.h
@@ -81,7 +81,6 @@ private Q_SLOTS:
 private:
     QInotifyFileSystemWatcherEngine(int fd);
     int inotifyFd;
-    QMutex mutex;
     QHash<QString, int> pathToID;
     QHash<int, QString> idToPath;
     QSocketNotifier notifier;
diff --git a/src/corelib/io/qfilesystemwatcher_kqueue.cpp b/src/corelib/io/qfilesystemwatcher_kqueue.cpp
index 1f16f6a226..8070af5e18 100644
--- a/src/corelib/io/qfilesystemwatcher_kqueue.cpp
+++ b/src/corelib/io/qfilesystemwatcher_kqueue.cpp
@@ -98,76 +98,72 @@ QStringList QKqueueFileSystemWatcherEngine::addPaths(const QStringList &paths,
                                                      QStringList *directories)
 {
     QStringList p = paths;
-    {
-        QMutexLocker locker(&mutex);
-
-        QMutableListIterator<QString> it(p);
-        while (it.hasNext()) {
-            QString path = it.next();
-            int fd;
+    QMutableListIterator<QString> it(p);
+    while (it.hasNext()) {
+        QString path = it.next();
+        int fd;
 #if defined(O_EVTONLY)
-            fd = qt_safe_open(QFile::encodeName(path), O_EVTONLY);
+        fd = qt_safe_open(QFile::encodeName(path), O_EVTONLY);
 #else
-            fd = qt_safe_open(QFile::encodeName(path), O_RDONLY);
+        fd = qt_safe_open(QFile::encodeName(path), O_RDONLY);
 #endif
-            if (fd == -1) {
-                perror("QKqueueFileSystemWatcherEngine::addPaths: open");
-                continue;
-            }
-            if (fd >= (int)FD_SETSIZE / 2 && fd < (int)FD_SETSIZE) {
-                int fddup = fcntl(fd, F_DUPFD, FD_SETSIZE);
-                if (fddup != -1) {
-                    ::close(fd);
-                    fd = fddup;
-                }
+        if (fd == -1) {
+            perror("QKqueueFileSystemWatcherEngine::addPaths: open");
+            continue;
+        }
+        if (fd >= (int)FD_SETSIZE / 2 && fd < (int)FD_SETSIZE) {
+            int fddup = fcntl(fd, F_DUPFD, FD_SETSIZE);
+            if (fddup != -1) {
+                ::close(fd);
+                fd = fddup;
             }
-            fcntl(fd, F_SETFD, FD_CLOEXEC);
+        }
+        fcntl(fd, F_SETFD, FD_CLOEXEC);
 
-            QT_STATBUF st;
-            if (QT_FSTAT(fd, &st) == -1) {
-                perror("QKqueueFileSystemWatcherEngine::addPaths: fstat");
+        QT_STATBUF st;
+        if (QT_FSTAT(fd, &st) == -1) {
+            perror("QKqueueFileSystemWatcherEngine::addPaths: fstat");
+            ::close(fd);
+            continue;
+        }
+        int id = (S_ISDIR(st.st_mode)) ? -fd : fd;
+        if (id < 0) {
+            if (directories->contains(path)) {
                 ::close(fd);
                 continue;
             }
-            int id = (S_ISDIR(st.st_mode)) ? -fd : fd;
-            if (id < 0) {
-                if (directories->contains(path)) {
-                    ::close(fd);
-                    continue;
-                }
-            } else {
-                if (files->contains(path)) {
-                    ::close(fd);
-                    continue;
-                }
-            }
-
-            struct kevent kev;
-            EV_SET(&kev,
-                   fd,
-                   EVFILT_VNODE,
-                   EV_ADD | EV_ENABLE | EV_CLEAR,
-                   NOTE_DELETE | NOTE_WRITE | NOTE_EXTEND | NOTE_ATTRIB | NOTE_RENAME | NOTE_REVOKE,
-                   0,
-                   0);
-            if (kevent(kqfd, &kev, 1, 0, 0, 0) == -1) {
-                perror("QKqueueFileSystemWatcherEngine::addPaths: kevent");
+        } else {
+            if (files->contains(path)) {
                 ::close(fd);
                 continue;
             }
+        }
 
-            it.remove();
-            if (id < 0) {
-                DEBUG() << "QKqueueFileSystemWatcherEngine: added directory path" << path;
-                directories->append(path);
-            } else {
-                DEBUG() << "QKqueueFileSystemWatcherEngine: added file path" << path;
-                files->append(path);
-            }
+        struct kevent kev;
+        EV_SET(&kev,
+               fd,
+               EVFILT_VNODE,
+               EV_ADD | EV_ENABLE | EV_CLEAR,
+               NOTE_DELETE | NOTE_WRITE | NOTE_EXTEND | NOTE_ATTRIB | NOTE_RENAME | NOTE_REVOKE,
+               0,
+               0);
+        if (kevent(kqfd, &kev, 1, 0, 0, 0) == -1) {
+            perror("QKqueueFileSystemWatcherEngine::addPaths: kevent");
+            ::close(fd);
+            continue;
+        }
 
-            pathToID.insert(path, id);
-            idToPath.insert(id, path);
+        it.remove();
+        if (id < 0) {
+            DEBUG() << "QKqueueFileSystemWatcherEngine: added directory path" << path;
+            directories->append(path);
+        } else {
+            DEBUG() << "QKqueueFileSystemWatcherEngine: added file path" << path;
+            files->append(path);
         }
+
+        pathToID.insert(path, id);
+        idToPath.insert(id, path);
     }
 
     return p;
@@ -179,29 +175,26 @@ QStringList QKqueueFileSystemWatcherEngine::removePaths(const QStringList &paths
 {
     bool isEmpty;
     QStringList p = paths;
-    {
-        QMutexLocker locker(&mutex);
-        if (pathToID.isEmpty())
-            return p;
-
-        QMutableListIterator<QString> it(p);
-        while (it.hasNext()) {
-            QString path = it.next();
-            int id = pathToID.take(path);
-            QString x = idToPath.take(id);
-            if (x.isEmpty() || x != path)
-                continue;
+    if (pathToID.isEmpty())
+        return p;
 
-            ::close(id < 0 ? -id : id);
+    QMutableListIterator<QString> it(p);
+    while (it.hasNext()) {
+        QString path = it.next();
+        int id = pathToID.take(path);
+        QString x = idToPath.take(id);
+        if (x.isEmpty() || x != path)
+            continue;
 
-            it.remove();
-            if (id < 0)
-                directories->removeAll(path);
-            else
-                files->removeAll(path);
-        }
-        isEmpty = pathToID.isEmpty();
+        ::close(id < 0 ? -id : id);
+
+        it.remove();
+        if (id < 0)
+            directories->removeAll(path);
+        else
+            files->removeAll(path);
     }
+    isEmpty = pathToID.isEmpty();
 
     return p;
 }
@@ -224,7 +217,6 @@ void QKqueueFileSystemWatcherEngine::readFromKqueue()
             int fd = kev.ident;
 
             DEBUG() << "QKqueueFileSystemWatcherEngine: processing kevent" << kev.ident << kev.filter;
-            QMutexLocker locker(&mutex);
 
             int id = fd;
             QString path = idToPath.value(id);
diff --git a/src/corelib/io/qfilesystemwatcher_kqueue_p.h b/src/corelib/io/qfilesystemwatcher_kqueue_p.h
index 6e36bcd8e5..41afbadf6a 100644
--- a/src/corelib/io/qfilesystemwatcher_kqueue_p.h
+++ b/src/corelib/io/qfilesystemwatcher_kqueue_p.h
@@ -85,7 +85,6 @@ private:
 
     int kqfd;
 
-    QMutex mutex;
     QHash<QString, int> pathToID;
     QHash<int, QString> idToPath;
     QSocketNotifier notifier;
diff --git a/src/corelib/io/qfilesystemwatcher_polling.cpp b/src/corelib/io/qfilesystemwatcher_polling.cpp
index 3d55c6d0aa..ef106acd0b 100644
--- a/src/corelib/io/qfilesystemwatcher_polling.cpp
+++ b/src/corelib/io/qfilesystemwatcher_polling.cpp
@@ -54,7 +54,6 @@ QStringList QPollingFileSystemWatcherEngine::addPaths(const QStringList &paths,
                                                       QStringList *files,
                                                       QStringList *directories)
 {
-    QMutexLocker locker(&mutex);
     QStringList p = paths;
     QMutableListIterator<QString> it(p);
     while (it.hasNext()) {
@@ -89,7 +88,6 @@ QStringList QPollingFileSystemWatcherEngine::removePaths(const QStringList &path
                                                          QStringList *files,
                                                          QStringList *directories)
 {
-    QMutexLocker locker(&mutex);
     QStringList p = paths;
     QMutableListIterator<QString> it(p);
     while (it.hasNext()) {
@@ -113,7 +111,6 @@ QStringList QPollingFileSystemWatcherEngine::removePaths(const QStringList &path
 
 void QPollingFileSystemWatcherEngine::timeout()
 {
-    QMutexLocker locker(&mutex);
     QMutableHashIterator<QString, FileInfo> fit(files);
     while (fit.hasNext()) {
         QHash<QString, FileInfo>::iterator x = fit.next();
diff --git a/src/corelib/io/qfilesystemwatcher_polling_p.h b/src/corelib/io/qfilesystemwatcher_polling_p.h
index 1fae542561..717d438582 100644
--- a/src/corelib/io/qfilesystemwatcher_polling_p.h
+++ b/src/corelib/io/qfilesystemwatcher_polling_p.h
@@ -105,7 +105,6 @@ class QPollingFileSystemWatcherEngine : public QFileSystemWatcherEngine
         }
     };
 
-    mutable QMutex mutex;
     QHash<QString, FileInfo> files, directories;
 
 public: