From f54ab5b17003b5fe721c88d443156bb209718ac7 Mon Sep 17 00:00:00 2001
From: James Cherry <cherry@parallaxsw.com>
Date: Sat, 17 Aug 2024 11:39:47 -0700
Subject: [PATCH] prima thread safety

Signed-off-by: James Cherry <cherry@parallaxsw.com>
---
 include/sta/Liberty.hh |  3 +++
 liberty/Liberty.cc     | 33 +++++++++++++++++++--------------
 2 files changed, 22 insertions(+), 14 deletions(-)

diff --git a/include/sta/Liberty.hh b/include/sta/Liberty.hh
index a18cceec..4763a8d0 100644
--- a/include/sta/Liberty.hh
+++ b/include/sta/Liberty.hh
@@ -16,6 +16,8 @@
 
 #pragma once
 
+#include <mutex>
+
 #include "MinMax.hh"
 #include "RiseFallMinMax.hh"
 #include "ConcreteLibrary.hh"
@@ -628,6 +630,7 @@ protected:
   LibertyPgPortMap pg_port_map_;
   bool has_internal_ports_;
   bool have_voltage_waveforms_;
+  std::mutex waveform_lock_;
 
 private:
   friend class LibertyLibrary;
diff --git a/liberty/Liberty.cc b/liberty/Liberty.cc
index 95a9cb48..ac15e702 100644
--- a/liberty/Liberty.cc
+++ b/liberty/Liberty.cc
@@ -16,6 +16,7 @@
 
 #include "Liberty.hh"
 
+#include "Mutex.hh"
 #include "EnumNameMap.hh"
 #include "Report.hh"
 #include "Debug.hh"
@@ -1963,24 +1964,28 @@ void
 LibertyCell::ensureVoltageWaveforms(const DcalcAnalysisPtSeq &dcalc_aps)
 {
   if (!have_voltage_waveforms_) {
-    float vdd = 0.0;  // shutup gcc
-    bool vdd_exists;
-    liberty_library_->supplyVoltage("VDD", vdd, vdd_exists);
-    if (!vdd_exists || vdd == 0.0)
-      criticalError(1120, "library missing vdd");
-    for (TimingArcSet *arc_set : timingArcSets()) {
-      for (TimingArc *arc : arc_set->arcs()) {
-        for (const DcalcAnalysisPt *dcalc_ap : dcalc_aps) {
-          GateTableModel *model = arc->gateTableModel(dcalc_ap);
-          if (model) {
-            OutputWaveforms *output_waveforms = model->outputWaveforms();
-            if (output_waveforms)
-              output_waveforms->ensureVoltageWaveforms(vdd);
+    LockGuard lock(waveform_lock_);
+    // Recheck with lock.
+    if (!have_voltage_waveforms_) {
+      float vdd = 0.0;  // shutup gcc
+      bool vdd_exists;
+      liberty_library_->supplyVoltage("VDD", vdd, vdd_exists);
+      if (!vdd_exists || vdd == 0.0)
+        criticalError(1120, "library missing vdd");
+      for (TimingArcSet *arc_set : timingArcSets()) {
+        for (TimingArc *arc : arc_set->arcs()) {
+          for (const DcalcAnalysisPt *dcalc_ap : dcalc_aps) {
+            GateTableModel *model = arc->gateTableModel(dcalc_ap);
+            if (model) {
+              OutputWaveforms *output_waveforms = model->outputWaveforms();
+              if (output_waveforms)
+                output_waveforms->ensureVoltageWaveforms(vdd);
+            }
           }
         }
       }
+      have_voltage_waveforms_ = true;
     }
-    have_voltage_waveforms_ = true;
   }
 }