src/libstore/build/derivation-goal.cc

@@ -58,8 +58,8 @@
 namespace nix {
 
 DerivationGoal::DerivationGoal(const StorePath & drvPath,
-    const OutputsSpec & wantedOutputs, Worker & worker, BuildMode buildMode)
-    : Goal(worker)
+    const OutputsSpec & wantedOutputs, Worker & worker, bool isDependency, BuildMode buildMode)
+    : Goal(worker, isDependency)
     , useDerivation(true)
     , drvPath(drvPath)
     , wantedOutputs(wantedOutputs)
@@ -76,8 +76,8 @@ DerivationGoal::DerivationGoal(const StorePath & drvPath,
 
 
 DerivationGoal::DerivationGoal(const StorePath & drvPath, const BasicDerivation & drv,
-    const OutputsSpec & wantedOutputs, Worker & worker, BuildMode buildMode)
-    : Goal(worker)
+    const OutputsSpec & wantedOutputs, Worker & worker, bool isDependency, BuildMode buildMode)
+    : Goal(worker, isDependency)
     , useDerivation(false)
     , drvPath(drvPath)
     , wantedOutputs(wantedOutputs)

src/libstore/build/derivation-goal.hh

@@ -234,10 +234,10 @@ struct DerivationGoal : public Goal
     std::string machineName;
 
     DerivationGoal(const StorePath & drvPath,
-        const OutputsSpec & wantedOutputs, Worker & worker,
+        const OutputsSpec & wantedOutputs, Worker & worker, bool isDependency,
         BuildMode buildMode = bmNormal);
     DerivationGoal(const StorePath & drvPath, const BasicDerivation & drv,
-        const OutputsSpec & wantedOutputs, Worker & worker,
+        const OutputsSpec & wantedOutputs, Worker & worker, bool isDependency,
         BuildMode buildMode = bmNormal);
     virtual ~DerivationGoal() noexcept(false);
 

src/libstore/build/drv-output-substitution-goal.cc

@@ -9,9 +9,10 @@ namespace nix {
 DrvOutputSubstitutionGoal::DrvOutputSubstitutionGoal(
     const DrvOutput & id,
     Worker & worker,
+    bool isDependency,
     RepairFlag repair,
     std::optional<ContentAddress> ca)
-    : Goal(worker)
+    : Goal(worker, isDependency)
     , id(id)
 {
     state = &DrvOutputSubstitutionGoal::init;

src/libstore/build/drv-output-substitution-goal.hh

@@ -56,7 +56,13 @@ class DrvOutputSubstitutionGoal : public Goal {
     bool substituterFailed = false;
 
 public:
-    DrvOutputSubstitutionGoal(const DrvOutput& id, Worker & worker, RepairFlag repair = NoRepair, std::optional<ContentAddress> ca = std::nullopt);
+    DrvOutputSubstitutionGoal(
+        const DrvOutput & id,
+        Worker & worker,
+        bool isDependency,
+        RepairFlag repair = NoRepair,
+        std::optional<ContentAddress> ca = std::nullopt
+    );
 
     typedef WorkResult (DrvOutputSubstitutionGoal::*GoalState)(bool inBuildSlot);
     GoalState state;

src/libstore/build/goal.hh

@@ -60,6 +60,13 @@ struct Goal
      */
     Worker & worker;
 
+    /**
+      * Whether this goal is only a dependency of other goals. Toplevel
+      * goals that are also dependencies of other toplevel goals do not
+      * set this, only goals that are exclusively dependencies do this.
+      */
+    const bool isDependency;
+
     /**
      * Goals that this goal is waiting for.
      */
@@ -143,8 +150,9 @@ public:
      */
     std::shared_ptr<Error> ex;
 
-    explicit Goal(Worker & worker)
+    explicit Goal(Worker & worker, bool isDependency)
         : worker(worker)
+        , isDependency(isDependency)
     { }
 
     virtual ~Goal() noexcept(false)

src/libstore/build/local-derivation-goal.hh

@@ -186,6 +186,7 @@ struct LocalDerivationGoal : public DerivationGoal
         const StorePath & drvPath,
         const OutputsSpec & wantedOutputs,
         Worker & worker,
+        bool isDependency,
         BuildMode buildMode
     );
 
@@ -198,6 +199,7 @@ struct LocalDerivationGoal : public DerivationGoal
         const BasicDerivation & drv,
         const OutputsSpec & wantedOutputs,
         Worker & worker,
+        bool isDependency,
         BuildMode buildMode
     );
 

src/libstore/build/substitution-goal.cc

@@ -6,8 +6,14 @@
 
 namespace nix {
 
-PathSubstitutionGoal::PathSubstitutionGoal(const StorePath & storePath, Worker & worker, RepairFlag repair, std::optional<ContentAddress> ca)
-    : Goal(worker)
+PathSubstitutionGoal::PathSubstitutionGoal(
+    const StorePath & storePath,
+    Worker & worker,
+    bool isDependency,
+    RepairFlag repair,
+    std::optional<ContentAddress> ca
+)
+    : Goal(worker, isDependency)
     , storePath(storePath)
     , repair(repair)
     , ca(ca)

src/libstore/build/substitution-goal.hh

@@ -80,7 +80,13 @@ struct PathSubstitutionGoal : public Goal
         std::optional<std::string> errorMsg = {});
 
 public:
-    PathSubstitutionGoal(const StorePath & storePath, Worker & worker, RepairFlag repair = NoRepair, std::optional<ContentAddress> ca = std::nullopt);
+    PathSubstitutionGoal(
+        const StorePath & storePath,
+        Worker & worker,
+        bool isDependency,
+        RepairFlag repair = NoRepair,
+        std::optional<ContentAddress> ca = std::nullopt
+    );
     ~PathSubstitutionGoal();
 
     Finished timedOut(Error && ex) override { abort(); };

src/libstore/build/worker.cc

@@ -1,5 +1,6 @@
 #include "charptr-cast.hh"
 #include "worker.hh"
+#include "finally.hh"
 #include "substitution-goal.hh"
 #include "drv-output-substitution-goal.hh"
 #include "local-derivation-goal.hh"
@@ -59,22 +60,38 @@ std::shared_ptr<DerivationGoal> Worker::makeDerivationGoalCommon(
 std::shared_ptr<DerivationGoal> Worker::makeDerivationGoal(const StorePath & drvPath,
     const OutputsSpec & wantedOutputs, BuildMode buildMode)
 {
-    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
-        return !dynamic_cast<LocalStore *>(&store)
-            ? std::make_shared<DerivationGoal>(drvPath, wantedOutputs, *this, buildMode)
-            : LocalDerivationGoal::makeLocalDerivationGoal(drvPath, wantedOutputs, *this, buildMode);
-    });
+    return makeDerivationGoalCommon(
+        drvPath,
+        wantedOutputs,
+        [&]() -> std::shared_ptr<DerivationGoal> {
+            return !dynamic_cast<LocalStore *>(&store)
+                ? std::make_shared<DerivationGoal>(
+                    drvPath, wantedOutputs, *this, running, buildMode
+                )
+                : LocalDerivationGoal::makeLocalDerivationGoal(
+                    drvPath, wantedOutputs, *this, running, buildMode
+                );
+        }
+    );
 }
 
 
 std::shared_ptr<DerivationGoal> Worker::makeBasicDerivationGoal(const StorePath & drvPath,
     const BasicDerivation & drv, const OutputsSpec & wantedOutputs, BuildMode buildMode)
 {
-    return makeDerivationGoalCommon(drvPath, wantedOutputs, [&]() -> std::shared_ptr<DerivationGoal> {
-        return !dynamic_cast<LocalStore *>(&store)
-            ? std::make_shared<DerivationGoal>(drvPath, drv, wantedOutputs, *this, buildMode)
-            : LocalDerivationGoal::makeLocalDerivationGoal(drvPath, drv, wantedOutputs, *this, buildMode);
-    });
+    return makeDerivationGoalCommon(
+        drvPath,
+        wantedOutputs,
+        [&]() -> std::shared_ptr<DerivationGoal> {
+            return !dynamic_cast<LocalStore *>(&store)
+                ? std::make_shared<DerivationGoal>(
+                    drvPath, drv, wantedOutputs, *this, running, buildMode
+                )
+                : LocalDerivationGoal::makeLocalDerivationGoal(
+                    drvPath, drv, wantedOutputs, *this, running, buildMode
+                );
+        }
+    );
 }
 
 
@@ -83,7 +100,7 @@ std::shared_ptr<PathSubstitutionGoal> Worker::makePathSubstitutionGoal(const Sto
     std::weak_ptr<PathSubstitutionGoal> & goal_weak = substitutionGoals[path];
     auto goal = goal_weak.lock(); // FIXME
     if (!goal) {
-        goal = std::make_shared<PathSubstitutionGoal>(path, *this, repair, ca);
+        goal = std::make_shared<PathSubstitutionGoal>(path, *this, running, repair, ca);
         goal_weak = goal;
         wakeUp(goal);
     }
@@ -96,7 +113,7 @@ std::shared_ptr<DrvOutputSubstitutionGoal> Worker::makeDrvOutputSubstitutionGoal
     std::weak_ptr<DrvOutputSubstitutionGoal> & goal_weak = drvOutputSubstitutionGoals[id];
     auto goal = goal_weak.lock(); // FIXME
     if (!goal) {
-        goal = std::make_shared<DrvOutputSubstitutionGoal>(id, *this, repair, ca);
+        goal = std::make_shared<DrvOutputSubstitutionGoal>(id, *this, running, repair, ca);
         goal_weak = goal;
         wakeUp(goal);
     }
@@ -313,6 +330,10 @@ void Worker::run(const Goals & _topGoals)
 {
     std::vector<nix::DerivedPath> topPaths;
 
+    assert(!running);
+    running = true;
+    Finally const _stop([&] { running = false; });
+
     for (auto & i : _topGoals) {
         topGoals.insert(i);
         if (auto goal = dynamic_cast<DerivationGoal *>(i.get())) {

src/libstore/build/worker.hh

@@ -47,6 +47,8 @@ class Worker
 {
 private:
 
+    bool running = false;
+
     /* Note: the worker should only have strong pointers to the
        top-level goals. */
 

src/libstore/platform.cc

@@ -29,17 +29,18 @@ std::shared_ptr<LocalDerivationGoal> LocalDerivationGoal::makeLocalDerivationGoa
     const StorePath & drvPath,
     const OutputsSpec & wantedOutputs,
     Worker & worker,
+    bool isDependency,
     BuildMode buildMode
 )
 {
 #if __linux__
-    return std::make_shared<LinuxLocalDerivationGoal>(drvPath, wantedOutputs, worker, buildMode);
+    return std::make_shared<LinuxLocalDerivationGoal>(drvPath, wantedOutputs, worker, isDependency, buildMode);
 #elif __APPLE__
-    return std::make_shared<DarwinLocalDerivationGoal>(drvPath, wantedOutputs, worker, buildMode);
+    return std::make_shared<DarwinLocalDerivationGoal>(drvPath, wantedOutputs, worker, isDependency, buildMode);
 #elif __FreeBSD__
-    return std::make_shared<FreeBSDLocalDerivationGoal>(drvPath, wantedOutputs, worker, buildMode);
+    return std::make_shared<FreeBSDLocalDerivationGoal>(drvPath, wantedOutputs, worker, isDependency, buildMode);
 #else
-    return std::make_shared<FallbackLocalDerivationGoal>(drvPath, wantedOutputs, worker, buildMode);
+    return std::make_shared<FallbackLocalDerivationGoal>(drvPath, wantedOutputs, worker, isDependency, buildMode);
 #endif
 }
 
@@ -48,24 +49,25 @@ std::shared_ptr<LocalDerivationGoal> LocalDerivationGoal::makeLocalDerivationGoa
     const BasicDerivation & drv,
     const OutputsSpec & wantedOutputs,
     Worker & worker,
+    bool isDependency,
     BuildMode buildMode
 )
 {
 #if __linux__
     return std::make_shared<LinuxLocalDerivationGoal>(
-        drvPath, drv, wantedOutputs, worker, buildMode
+        drvPath, drv, wantedOutputs, worker, isDependency, buildMode
     );
 #elif __APPLE__
     return std::make_shared<DarwinLocalDerivationGoal>(
-        drvPath, drv, wantedOutputs, worker, buildMode
+        drvPath, drv, wantedOutputs, worker, isDependency, buildMode
     );
 #elif __FreeBSD__
     return std::make_shared<FreeBSDLocalDerivationGoal>(
-        drvPath, drv, wantedOutputs, worker, buildMode
+        drvPath, drv, wantedOutputs, worker, isDependency, buildMode
     );
 #else
     return std::make_shared<FallbackLocalDerivationGoal>(
-        drvPath, drv, wantedOutputs, worker, buildMode
+        drvPath, drv, wantedOutputs, worker, isDependency, buildMode
     );
 #endif
 }