RemoteLinux: Cache device environment

Change-Id: Ida735b69179b418c21d3875c3906b9449709623a
Reviewed-by: hjk <hjk@qt.io>

src/plugins/remotelinux/linuxdevice.cpp

@@ -37,6 +37,7 @@
 #include <QDateTime>
 #include <QLoggingCategory>
 #include <QMutex>
+#include <QReadWriteLock>
 #include <QRegularExpression>
 #include <QScopeGuard>
 #include <QTemporaryDir>
@@ -376,14 +377,49 @@ public:
     void attachToSharedConnection(SshConnectionHandle *connectionHandle,
                                   const SshParameters &sshParameters);
 
+    Environment getEnvironment();
+    void invalidateEnvironmentCache();
+
     LinuxDevice *q = nullptr;
     QThread m_shellThread;
     ShellThreadHandler *m_handler = nullptr;
     mutable QMutex m_shellMutex;
     QList<QtcProcess *> m_terminals;
     LinuxDeviceFileAccess m_fileAccess{this};
+
+    QReadWriteLock m_environmentCacheLock;
+    std::optional<Environment> m_environmentCache;
 };
 
+void LinuxDevicePrivate::invalidateEnvironmentCache()
+{
+    QWriteLocker locker(&m_environmentCacheLock);
+    m_environmentCache.reset();
+}
+
+Environment LinuxDevicePrivate::getEnvironment()
+{
+    QReadLocker locker(&m_environmentCacheLock);
+    if (m_environmentCache.has_value())
+        return m_environmentCache.value();
+
+    locker.unlock();
+    QWriteLocker writeLocker(&m_environmentCacheLock);
+    if (m_environmentCache.has_value())
+        return m_environmentCache.value();
+
+    QtcProcess getEnvProc;
+    getEnvProc.setCommand({FilePath("env").onDevice(q->rootPath()), {}});
+    Environment inEnv;
+    inEnv.setCombineWithDeviceEnvironment(false);
+    getEnvProc.setEnvironment(inEnv);
+    getEnvProc.runBlocking();
+
+    const QString remoteOutput = getEnvProc.cleanedStdOut();
+    m_environmentCache = Environment(remoteOutput.split('\n', Qt::SkipEmptyParts), q->osType());
+    return m_environmentCache.value();
+}
+
 RunResult LinuxDeviceFileAccess::runInShell(const CommandLine &cmdLine,
                                             const QByteArray &stdInData) const
 {
@@ -392,15 +428,7 @@ RunResult LinuxDeviceFileAccess::runInShell(const CommandLine &cmdLine,
 
 Environment LinuxDeviceFileAccess::deviceEnvironment() const
 {
-    QtcProcess getEnvProc;
+    return m_dev->getEnvironment();
-    getEnvProc.setCommand({FilePath("env").onDevice(m_dev->q->rootPath()), {}});
-    Environment inEnv;
-    inEnv.setCombineWithDeviceEnvironment(false);
-    getEnvProc.setEnvironment(inEnv);
-    getEnvProc.runBlocking();
-
-    const QString remoteOutput = getEnvProc.cleanedStdOut();
-    return Environment(remoteOutput.split('\n', Qt::SkipEmptyParts), m_dev->q->osType());
 }
 
 // SshProcessImpl
@@ -1126,6 +1154,8 @@ bool LinuxDevicePrivate::setupShell()
     if (m_handler->isRunning(sshParameters))
         return true;
 
+    invalidateEnvironmentCache();
+
     bool ok = false;
     QMetaObject::invokeMethod(m_handler, [this, sshParameters] {
         return m_handler->start(sshParameters);