SolarMutex::m_nThreadId is read without SolarMutex::m_aMutex locked

...so better make it std::atomic<> (and it also can be private).  And in
SolarMutex::doRelease, make sure that m_nCount is only read with m_aMutex
locked.

Change-Id: Iee0c1465e60e07ccd8955010a3dbc15a99dbe807
Reviewed-on: https://gerrit.libreoffice.org/71260
Tested-by: Jenkins
Reviewed-by: Stephan Bergmann <sbergman@redhat.com>

comphelper/source/misc/solarmutex.cxx

@@ -60,9 +60,9 @@ void SolarMutex::doAcquire( const sal_uInt32 nLockCount )
 
 sal_uInt32 SolarMutex::doRelease( bool bUnlockAll )
 {
-    if ( m_nCount == 0 )
+    if ( !IsCurrentThread() )
         std::abort();
-    if ( m_nThreadId != osl::Thread::getCurrentIdentifier() )
+    if ( m_nCount == 0 )
         std::abort();
 
     const sal_uInt32 nCount = bUnlockAll ? m_nCount : 1;

include/comphelper/solarmutex.hxx

@@ -23,6 +23,8 @@
 #include <sal/config.h>
 
 #include <assert.h>
+#include <atomic>
+
 #include <osl/thread.h>
 #include <osl/mutex.hxx>
 #include <comphelper/comphelperdllapi.h>
@@ -68,9 +70,10 @@ protected:
 
     osl::Mutex            m_aMutex;
     sal_uInt32            m_nCount;
-    oslThreadIdentifier   m_nThreadId;
 
 private:
+    std::atomic<oslThreadIdentifier> m_nThreadId;
+
     SolarMutex(const SolarMutex&) = delete;
     SolarMutex& operator=(const SolarMutex&) = delete;