obv patch: debuginfod concurrency fix

[Frank Ch. Eigler]

Hi -

Committing as obvious.

Author: Frank Ch. Eigler <fche@redhat.com>
Date:   Wed Dec 8 10:20:58 2021 -0500

    debuginfod: correct concurrency bug in fdcache metrics
    
    The intern() function called set_metrics() outside a necessary lock
    being held.  helgrind identified this race condition.  No QA impact.
    
    Signed-off-by: Frank Ch. Eigler <fche@redhat.com>

diff --git a/debuginfod/ChangeLog b/debuginfod/ChangeLog
index 8c937d6629a3..8cbaa9aa6fd9 100644
--- a/debuginfod/ChangeLog
+++ b/debuginfod/ChangeLog
@@ -1,3 +1,7 @@
+2021-12-08  Frank Ch. Eigler  <fche@redhat.com>
+
+	* debuginfod.cxx (intern): Call set_metrics() holding the fdcache mutex.
+
 2021-12-04  Mark Wielaard  <mark@klomp.org>
 
 	* debuginfod-client.c (debuginfod_query_server): Free winning_headers.
diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
index 0d3f02978ee2..a26e7e8fce37 100644
--- a/debuginfod/debuginfod.cxx
+++ b/debuginfod/debuginfod.cxx
@@ -1354,8 +1354,8 @@ class libarchive_fdcache
       if (verbose > 3)
         obatched(clog) << "fdcache interned a=" << a << " b=" << b
                        << " fd=" << fd << " mb=" << mb << " front=" << front_p << endl;
+      set_metrics();
     }
-    set_metrics();
 
     // NB: we age the cache at lookup time too
     if (statfs_free_enough_p(tmpdir, "tmpdir", fdcache_mintmp))