From 3dfdda667a2c8b950e09d26b06721bf930d4f39e Mon Sep 17 00:00:00 2001
From: Michael Davidsaver <mdavidsaver@gmail.com>
Date: Wed, 29 Nov 2017 09:48:54 -0600
Subject: [PATCH] avoid possible lock order issue with interested_remove

Ensure that Monitors aren't destroy()'d with an extra,
unnecessary, lock held.
---
 pdbApp/pdbgroup.cpp  | 10 ++++++----
 pdbApp/pdbsingle.cpp | 10 ++++++----
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/pdbApp/pdbgroup.cpp b/pdbApp/pdbgroup.cpp
index 75efc50..bfa8b0a 100644
--- a/pdbApp/pdbgroup.cpp
+++ b/pdbApp/pdbgroup.cpp
@@ -82,6 +82,7 @@ void pdb_group_event(void *user_arg, struct dbChannel *chan,
                 mon.post(self->scratch);
             }
 
+            PDBGroupPV::interested_remove_t temp;
             {
                 Guard G(self->lock);
 
@@ -93,10 +94,11 @@ void pdb_group_event(void *user_arg, struct dbChannel *chan,
                     self->interested_add.erase(first);
                 }
 
-                while(!self->interested_remove.empty()) {
-                    PDBGroupPV::interested_remove_t::iterator first(self->interested_remove.begin());
-                    self->interested.erase(static_cast<PDBGroupMonitor*>(first->get()));
-                    self->interested_remove.erase(first);
+                temp.swap(self->interested_remove);
+                for(PDBGroupPV::interested_remove_t::iterator it(temp.begin()),
+                    end(temp.end()); it != end; ++it)
+                {
+                    self->interested.erase(static_cast<PDBGroupMonitor*>(it->get()));
                 }
 
                 self->interested_iterating = false;
diff --git a/pdbApp/pdbsingle.cpp b/pdbApp/pdbsingle.cpp
index 548cf8f..07d3be6 100644
--- a/pdbApp/pdbsingle.cpp
+++ b/pdbApp/pdbsingle.cpp
@@ -61,6 +61,7 @@ void pdb_single_event(void *user_arg, struct dbChannel *chan,
                 mon.post(self->scratch);
             }
 
+            PDBSinglePV::interested_remove_t temp;
             {
                 Guard G(self->lock);
 
@@ -72,10 +73,11 @@ void pdb_single_event(void *user_arg, struct dbChannel *chan,
                     self->interested_add.erase(first);
                 }
 
-                while(!self->interested_remove.empty()) {
-                    PDBSinglePV::interested_remove_t::iterator first(self->interested_remove.begin());
-                    self->interested.erase(static_cast<PDBSingleMonitor*>(first->get()));
-                    self->interested_remove.erase(first);
+                temp.swap(self->interested_remove);
+                for(PDBSinglePV::interested_remove_t::iterator it(temp.begin()),
+                    end(temp.end()); it != end; ++it)
+                {
+                    self->interested.erase(static_cast<PDBSingleMonitor*>(it->get()));
                 }
 
                 self->interested_iterating = false;