From 7f8d348f3ddee2161331c0ecc89c7780272c48b1 Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 16 Mar 2025 18:32:20 -0400
Subject: [PATCH 1/2] Move `derivationType` from `DerivationGoal` to
 `LocalDerivationGoal`

The super class doesn't actually care.
---
 src/libstore/build/derivation-goal.cc            |  3 ---
 src/libstore/build/derivation-goal.hh            |  5 -----
 src/libstore/unix/build/local-derivation-goal.cc | 10 +++++++++-
 3 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index 907d7f8eb..c49b52e8d 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -533,9 +533,6 @@ Goal::Co DerivationGoal::gaveUpOnSubstitution()
 
     debug("added input paths %s", worker.store.showPaths(inputPaths));
 
-    /* What type of derivation are we building? */
-    derivationType = drv->type();
-
     /* Okay, try to build.  Note that here we don't wait for a build
        slot to become available, since we don't need one if there is a
        build hook. */
diff --git a/src/libstore/build/derivation-goal.hh b/src/libstore/build/derivation-goal.hh
index 25ab90183..f95f10b39 100644
--- a/src/libstore/build/derivation-goal.hh
+++ b/src/libstore/build/derivation-goal.hh
@@ -198,11 +198,6 @@ struct DerivationGoal : public Goal
     std::unique_ptr<HookInstance> hook;
 #endif
 
-    /**
-     * The sort of derivation we are building.
-     */
-    std::optional<DerivationType> derivationType;
-
     BuildMode buildMode;
 
     std::unique_ptr<MaintainCount<uint64_t>> mcExpectedBuilds, mcRunningBuilds;
diff --git a/src/libstore/unix/build/local-derivation-goal.cc b/src/libstore/unix/build/local-derivation-goal.cc
index 371d94b95..a3015480d 100644
--- a/src/libstore/unix/build/local-derivation-goal.cc
+++ b/src/libstore/unix/build/local-derivation-goal.cc
@@ -150,6 +150,13 @@ struct LocalDerivationGoal : DerivationGoal, RestrictionContext
      */
     std::shared_ptr<AutoDelete> autoDelChroot;
 
+    /**
+     * The sort of derivation we are building.
+     *
+     * Just a cached value, can be recomputed from `drv`.
+     */
+    std::optional<DerivationType> derivationType;
+
     /**
      * Stuff we need to pass to initChild().
      */
@@ -478,7 +485,8 @@ Goal::Co LocalDerivationGoal::tryLocalBuild()
         co_return tryToBuild();
     }
 
-    assert(derivationType);
+    /* Cache this */
+    derivationType = drv->type();
 
     /* Are we doing a chroot build? */
     {

From 1c022077ead393b8624742202b002f9a8c041a1d Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Sun, 16 Mar 2025 19:21:21 -0400
Subject: [PATCH 2/2] Get rid of on usage pair of `actLock`

Now that we have coroutines, we can go back to loops and regular RAII,
which is must less error-proone!

I look forward to removing the other instances!
---
 src/libstore/build/derivation-goal.cc | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/libstore/build/derivation-goal.cc b/src/libstore/build/derivation-goal.cc
index c49b52e8d..4978eecd2 100644
--- a/src/libstore/build/derivation-goal.cc
+++ b/src/libstore/build/derivation-goal.cc
@@ -594,16 +594,18 @@ Goal::Co DerivationGoal::tryToBuild()
         }
     }
 
-    if (!outputLocks.lockPaths(lockFiles, "", false)) {
-        if (!actLock)
-            actLock = std::make_unique<Activity>(*logger, lvlWarn, actBuildWaiting,
+    if (!outputLocks.lockPaths(lockFiles, "", false))
+    {
+        Activity act(*logger, lvlWarn, actBuildWaiting,
                 fmt("waiting for lock on %s", Magenta(showPaths(lockFiles))));
-        worker.waitForAWhile(shared_from_this());
-        co_await Suspend{};
-        co_return tryToBuild();
-    }
 
-    actLock.reset();
+        /* Wait then try locking again, repeat until success (returned
+           boolean is true). */
+        do {
+            worker.waitForAWhile(shared_from_this());
+            co_await Suspend{};
+        } while (!outputLocks.lockPaths(lockFiles, "", false));
+    }
 
     /* Now check again whether the outputs are valid.  This is because
        another process may have started building in parallel.  After