From: Brad Hubbard <bhubbard@redhat.com>
Date: Wed, 30 Jul 2025 23:12:23 +0000 (+1000)
Subject: mgr/DaemonState: Minimise time we hold the DaemonStateIndex lock
X-Git-Url: http://git-server-git.apps.pok.os.sepia.ceph.com/?a=commitdiff_plain;h=2d227ab51fd72313fb359a0bf7b53722fe793fbc;p=ceph.git

mgr/DaemonState: Minimise time we hold the DaemonStateIndex lock

Calling back into python functions whilst holding the lock can result in
this thread being queued for the GIL and resulting in extended delays
for threads waiting to acquire the lock.

Fixes: https://tracker.ceph.com/issues/72337
Signed-off-by: Brad Hubbard <bhubbard@redhat.com>
(cherry picked from commit b4304d521f61b61515cade872824210e7d67f6db)
---

diff --git a/src/mgr/DaemonState.h b/src/mgr/DaemonState.h
index d78e819405b0..960cbcbd3026 100644
--- a/src/mgr/DaemonState.h
+++ b/src/mgr/DaemonState.h
@@ -261,9 +261,12 @@ public:
   template<typename Callback, typename...Args>
   auto with_daemons_by_server(Callback&& cb, Args&&... args) const ->
     decltype(cb(by_server, std::forward<Args>(args)...)) {
-    std::shared_lock l{lock};
-    
-    return std::forward<Callback>(cb)(by_server, std::forward<Args>(args)...);
+    const decltype(by_server) by_server_copy = [&] {
+      // Don't hold the lock any longer than necessary
+      std::shared_lock l{lock};
+      return by_server;
+    }();
+    return std::forward<Callback>(cb)(by_server_copy, std::forward<Args>(args)...);
   }
 
   template<typename Callback, typename...Args>