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

@@ -268,39 +268,46 @@ bool ProcStats::fetch( procInfo& f ) {
   int        cnt{0};
   char       buf[500];
 
-  m_ufd.lseek( 0, SEEK_SET );
-
-  if ( ( cnt = m_ufd.read( buf, sizeof( buf ) ) ) < 0 ) {
-    std::cerr << "ProcStats : LINUX Read of Proc file failed:" << std::endl;
-    return false;
+  auto read_proc = [&]() {
+    m_ufd.lseek( 0, SEEK_SET );
+    if ( ( cnt = m_ufd.read( buf, sizeof( buf ) ) ) < 0 ) {
+      std::cerr << "ProcStats : LINUX Read of Proc file failed:" << std::endl;
+      return false;
+    }
+    if ( cnt > 0 ) {
+      buf[std::min( static_cast<std::size_t>( cnt ), sizeof( buf ) - 1 )] = '\0';
+      sscanf(
+          buf,
+          // 1  2  3  4  5  6  7  8  9  10  1   2   3   4   5   6   7   8   9   20  1   2   3   4   5   6   7   8   9
+          // 30  1   2   3   4   5
+          "%d %s %c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld %llu %lu %ld %lu %lu %lu %lu "
+          "%lu %lu %lu %lu %lu %lu %lu",
+          &pinfo.pid, pinfo.comm, &pinfo.state, &pinfo.ppid, &pinfo.pgrp, &pinfo.session, &pinfo.tty, &pinfo.tpgid,
+          &pinfo.flags, &pinfo.minflt, &pinfo.cminflt, &pinfo.majflt, &pinfo.cmajflt, &pinfo.utime, &pinfo.stime,
+          &pinfo.cutime, &pinfo.cstime, &pinfo.priority, &pinfo.nice, &pinfo.num_threads, &pinfo.itrealvalue,
+          &pinfo.starttime, &pinfo.vsize, &pinfo.rss, &pinfo.rlim, &pinfo.startcode, &pinfo.endcode, &pinfo.startstack,
+          &pinfo.kstkesp, &pinfo.kstkeip, &pinfo.signal, &pinfo.blocked, &pinfo.sigignore, &pinfo.sigcatch,
+          &pinfo.wchan );
+      // resident set size in pages
+      pr_size   = (double)pinfo.vsize;
+      pr_rssize = (double)pinfo.rss;
+      f.vsize   = pr_size / ( 1024 * 1024 );
+      f.rss     = pr_rssize * m_pg_size / ( 1024 * 1024 );
+    }
+    return true;
+  };
+
+  // attempt to read from proc
+  if ( !read_proc() ) {
+    std::cerr << "ProcStats : -> Will try reopening process proc stats" << std::endl;
+    open_ufd();
+    if ( !read_proc() ) { return false; }
   }
 
-  if ( cnt > 0 ) {
-    buf[std::min( static_cast<std::size_t>( cnt ), sizeof( buf ) - 1 )] = '\0';
-
-    sscanf( buf,
-            // 1  2  3  4  5  6  7  8  9  10  1   2   3   4   5   6   7   8   9   20  1   2   3   4   5   6   7   8   9
-            // 30  1   2   3   4   5
-            "%d %s %c %d %d %d %d %d %lu %lu %lu %lu %lu %lu %lu %ld %ld %ld %ld %ld %ld %llu %lu %ld %lu %lu %lu %lu "
-            "%lu %lu %lu %lu %lu %lu %lu",
-            &pinfo.pid, pinfo.comm, &pinfo.state, &pinfo.ppid, &pinfo.pgrp, &pinfo.session, &pinfo.tty, &pinfo.tpgid,
-            &pinfo.flags, &pinfo.minflt, &pinfo.cminflt, &pinfo.majflt, &pinfo.cmajflt, &pinfo.utime, &pinfo.stime,
-            &pinfo.cutime, &pinfo.cstime, &pinfo.priority, &pinfo.nice, &pinfo.num_threads, &pinfo.itrealvalue,
-            &pinfo.starttime, &pinfo.vsize, &pinfo.rss, &pinfo.rlim, &pinfo.startcode, &pinfo.endcode,
-            &pinfo.startstack, &pinfo.kstkesp, &pinfo.kstkeip, &pinfo.signal, &pinfo.blocked, &pinfo.sigignore,
-            &pinfo.sigcatch, &pinfo.wchan );
-
-    // resident set size in pages
-    pr_size   = (double)pinfo.vsize;
-    pr_rssize = (double)pinfo.rss;
-
-    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();
-    }
+  if ( 0 == pinfo.vsize ) {
+    std::cerr << "ProcStats : 0==vsize -> Will try reopening process proc stats" << std::endl;
+    open_ufd();
+    if ( !read_proc() ) { return false; }
   }
 
 #else