ProcStats : Use mutex lock to make fetch() thread safe.

Whilst investigating a possible memory issue using the Memory Auditor, I discovered the information printed was garbled if multiple threads where used.

The issue was the ProcStats::fetch method which was not thread safe. This MR fixes that with a simple mutex lock.

I also did a drive-by cleanup and code modernisation.

FYI @clemenci

GaudiAud/src/ProcStats.cpp

@@ -259,13 +259,13 @@ void ProcStats::open_ufd() {
 bool ProcStats::fetch( procInfo& f ) {
   if ( !m_valid ) { return false; }
 
-  std::scoped_lock lock{m_mutex};
+  std::scoped_lock lock{ m_mutex };
 
 #if defined( __linux__ ) or defined( __APPLE__ )
 
-  double     pr_size{0}, pr_rssize{0};
+  double     pr_size{ 0 }, pr_rssize{ 0 };
   linux_proc pinfo;
-  int        cnt{0};
+  int        cnt{ 0 };
   char       buf[500];
 
   m_ufd.lseek( 0, SEEK_SET );
@@ -296,6 +296,11 @@ bool ProcStats::fetch( procInfo& f ) {
 
     f.vsize = pr_size / ( 1024 * 1024 );
     f.rss   = pr_rssize * m_pg_size / ( 1024 * 1024 );
+
+    if ( 0 == pinfo.vsize ) {
+      std::cerr << "ProcStats : 0==vsize -> Will try reopening process proc stats" << std::endl;
+      open_ufd();
+    }
   }
 
 #else
@@ -308,10 +313,5 @@ bool ProcStats::fetch( procInfo& f ) {
   m_curr.rss   = f.rss;
   m_curr.vsize = f.vsize;
 
-  if ( 0 == m_curr.vsize ) {
-    std::cerr << "ProcStats : 0==vsize -> Will try reopening process proc stats" << std::endl;
-    open_ufd();
-  }
-
   return rc;
 }