QSampleCache: Wait for load thread to finish before restarting it

One cannot rely on QThread::isRunning for checking whether the thread
hasn't finished yet, as the thread might be quitting and still return
true from isRunning. In that case, the thread won't process the sample
load request that misses the start() call in this case.

Fixes: QTBUG-109167
Pick-to: 6.5
Change-Id: I33382ad3d8a19ceb86857c51227e81a86a88eea7
Reviewed-by: Lars Knoll <lars@knoll.priv.no>

1 files changed, 5 insertions, 1 deletions

diff --git a/src/multimedia/audio/qsamplecache_p.cpp b/src/multimedia/audio/qsamplecache_p.cpp
index e753402fb..825c79685 100644
--- a/src/multimedia/audio/qsamplecache_p.cpp
+++ b/src/multimedia/audio/qsamplecache_p.cpp
@@ -130,6 +130,7 @@ QSample* QSampleCache::requestSample(const QUrl& url)
 {
     //lock and add first to make sure live loadingThread will not be killed during this function call
     m_loadingMutex.lock();
+    const bool needsThreadStart = m_loadingRefCount == 0;
     m_loadingRefCount++;
     m_loadingMutex.unlock();
 
@@ -138,8 +139,11 @@ QSample* QSampleCache::requestSample(const QUrl& url)
     QMap<QUrl, QSample*>::iterator it = m_samples.find(url);
     QSample* sample;
     if (it == m_samples.end()) {
-        if (!m_loadingThread.isRunning())
+        if (needsThreadStart) {
+            // Previous thread might be finishing, need to wait for it. If not, this is a no-op.
+            m_loadingThread.wait();
             m_loadingThread.start();
+        }
         sample = new QSample(url, this);
         m_samples.insert(url, sample);
 #if QT_CONFIG(thread)