eliminate seperate mutex for BaseMonitor

common/pvahelper.h

@@ -74,7 +74,7 @@ struct BaseMonitor : public epics::pvAccess::Monitor
 
     typedef epics::pvAccess::MonitorRequester requester_t;
 
-    mutable epicsMutex lock; // not held during any callback
+    epicsMutex& lock; // not held during any callback
     typedef epicsGuard<epicsMutex> guard_t;
 
 private:
@@ -90,9 +90,11 @@ private:
     buffer_t inuse, empty;
 
 public:
-    BaseMonitor(const requester_t::weak_pointer& requester,
+    BaseMonitor(epicsMutex& lock,
+                const requester_t::weak_pointer& requester,
                 const epics::pvData::PVStructure::shared_pointer& pvReq)
-        :requester(requester)
+        :lock(lock)
+        ,requester(requester)
         ,inoverflow(false)
         ,running(false)
         ,nbuffers(2)

pdbApp/pdbgroup.cpp

@@ -416,7 +416,7 @@ void PDBGroupPut::get()
 PDBGroupMonitor::PDBGroupMonitor(const PDBGroupPV::shared_pointer& pv,
                  const epics::pvAccess::MonitorRequester::weak_pointer &requester,
                  const pvd::PVStructure::shared_pointer& pvReq)
-    :BaseMonitor(requester, pvReq)
+    :BaseMonitor(pv->lock, requester, pvReq)
     ,pv(pv)
 {
     epics::atomic::increment(num_instances);

pdbApp/pdbsingle.cpp

@@ -55,6 +55,7 @@ void pdb_single_event(void *user_arg, struct dbChannel *chan,
             self->scratch.clear();
             {
                 DBScanLocker L(dbChannelRecord(self->chan));
+                // dbGet() into self->complete
                 self->pvif->put(self->scratch, evt->dbe_mask, pfl);
             }
 
@@ -63,6 +64,7 @@ void pdb_single_event(void *user_arg, struct dbChannel *chan,
 
             FOREACH(PDBSinglePV::interested_t::const_iterator, it, end, self->interested) {
                 PDBSingleMonitor& mon = **it;
+                // from self->complete into monitor queue element
                 mon.post(self->scratch);
             }
 
@@ -433,7 +435,7 @@ void PDBSinglePut::get()
 PDBSingleMonitor::PDBSingleMonitor(const PDBSinglePV::shared_pointer& pv,
                  const requester_t::shared_pointer& requester,
                  const pvd::PVStructure::shared_pointer& pvReq)
-    :BaseMonitor(requester, pvReq)
+    :BaseMonitor(pv->lock, requester, pvReq)
     ,pv(pv)
 {
     epics::atomic::increment(num_instances);