QMutex symbian review changes

Improved documentation
Added a trywait(0) test and fixed the bug it found
Symbian implementation throws on construction fail

Task-number: QTBUG-13990
Reviewed-by: Shane Kearns

2 files changed, 6 insertions, 1 deletions

diff --git a/src/corelib/thread/qmutex_p.h b/src/corelib/thread/qmutex_p.h
index c213c80b52..2588228ff8 100644
--- a/src/corelib/thread/qmutex_p.h
+++ b/src/corelib/thread/qmutex_p.h
@@ -98,8 +98,11 @@ public:
     HANDLE event;
 #elif defined(Q_OS_SYMBIAN)
 # ifdef QT_SYMBIAN_USE_RFASTLOCK
+    // RFastLock is a fast semaphone which only calls into the kernel side if there is contention
     RFastLock lock;
 # else
+    // RSemaphore is used on Symbian OS versions that do not have a timed RFastLock wait.
+    // There is no timed wait on RMutex itself, so RSemaphore has to be used instead.
     RSemaphore lock;
 # endif
 #endif
diff --git a/src/corelib/thread/qmutex_symbian.cpp b/src/corelib/thread/qmutex_symbian.cpp
index e7487cd675..09c59af190 100644
--- a/src/corelib/thread/qmutex_symbian.cpp
+++ b/src/corelib/thread/qmutex_symbian.cpp
@@ -62,6 +62,7 @@ QMutexPrivate::QMutexPrivate(QMutex::RecursionMode mode)
 #endif
     if (r != KErrNone)
         qWarning("QMutex: failed to create lock, error %d", r);
+    qt_symbian_throwIfError(r);
 }
 
 QMutexPrivate::~QMutexPrivate()
@@ -86,7 +87,8 @@ bool QMutexPrivate::wait(int timeout)
         do {
             int waitTime = qMin(KMaxTInt / 1000, timeout);
             timeout -= waitTime;
-            r = lock.Wait(waitTime * 1000);
+            // Symbian undocumented feature - 0us means no timeout! Use a minimum of 1
+            r = lock.Wait(qMax(1, waitTime * 1000));
         } while (r != KErrNone && r != KErrGeneral && r != KErrArgument && timeout > 0);
     }
     bool returnValue = (r == KErrNone);