From: Otto Moerbeek <otto.moerbeek@open-xchange.com>
Date: Wed, 27 Mar 2024 10:08:46 +0000 (+0100)
Subject: Explain the d_cachedir_mutex is only used for protecting init() calls
X-Git-Tag: rec-5.1.0-alpha1~77^2
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=refs%2Fpull%2F13969%2Fhead;p=thirdparty%2Fpdns.git

Explain the d_cachedir_mutex is only used for protecting init() calls
---

diff --git a/pdns/recursordist/nod.hh b/pdns/recursordist/nod.hh
index fb59c35100..1cc8f456dc 100644
--- a/pdns/recursordist/nod.hh
+++ b/pdns/recursordist/nod.hh
@@ -69,7 +69,10 @@ private:
   LockGuarded<bf::stableBF> d_sbf; // Stable Bloom Filter
   std::string d_cachedir;
   std::string d_prefix = sbf_prefix;
-  static std::mutex d_cachedir_mutex; // One mutex for all instances of this class
+  // One mutex for all instances of this class, used to avoid multiple init() calls happening
+  // simulateneously.  The snapshot code is thread safe wrt file operations, so it does not need to
+  // acquire this mutex, assuming the init() code never runs simulatenously with the snapshot code.
+  static std::mutex d_cachedir_mutex;
 };
 
 class NODDB