From 824b154ce82a76bfc604b3084b18e06af4e3d007 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Mon, 16 Feb 2009 09:24:20 +0000
Subject: [PATCH] * Release output locks as soon as possible, not when the
 destructor of   the DerivationGoal runs.  Otherwise, if a goal is a top-level
 goal,   then the lock won't be released until nix-store finishes.  With  
 --keep-going and lots of top-level goals, it's possible to run out   of file
 descriptors (this happened sometimes in the build farm for   Nixpkgs).  Also,
 for failed derivation, it won't be possible to   build it again  until the
 lock is released.

* Idem for locks on build users: these weren't released in a timely
  manner for failed top-level derivation goals.  So if there were more
  than (say) 10 such failed builds, you would get an error about
  having run out of build users.
---
 src/libstore/build.cc     | 5 +++++
 src/libstore/pathlocks.cc | 8 ++++++++
 src/libstore/pathlocks.hh | 1 +
 3 files changed, 14 insertions(+)

diff --git a/src/libstore/build.cc b/src/libstore/build.cc
index d44dcf0ff..5f1eb3415 100644
--- a/src/libstore/build.cc
+++ b/src/libstore/build.cc
@@ -1023,6 +1023,8 @@ void DerivationGoal::tryToBuild()
 
     } catch (BuildError & e) {
         printMsg(lvlError, e.msg());
+        outputLocks.unlock();
+        buildUser.release();
         if (printBuildTrace) {
             if (usingBuildHook)
                 printMsg(lvlError, format("@ hook-failed %1% %2% %3% %4%")
@@ -1130,6 +1132,8 @@ void DerivationGoal::buildDone()
 
     } catch (BuildError & e) {
         printMsg(lvlError, e.msg());
+        outputLocks.unlock();
+        buildUser.release();
         if (printBuildTrace) {
             /* When using a build hook, the hook will return a
                remote build failure using exit code 100.  Anything
@@ -2068,6 +2072,7 @@ void DerivationGoal::computeClosure()
        create new lock files with the same names as the old (unlinked)
        lock files. */
     outputLocks.setDeletion(true);
+    outputLocks.unlock();
 }
 
 
diff --git a/src/libstore/pathlocks.cc b/src/libstore/pathlocks.cc
index df1f0b1e3..f8753bcb6 100644
--- a/src/libstore/pathlocks.cc
+++ b/src/libstore/pathlocks.cc
@@ -203,6 +203,12 @@ void PathLocks::lockPaths(const PathSet & _paths, const string & waitMsg)
 
 
 PathLocks::~PathLocks()
+{
+    unlock();
+}
+
+
+void PathLocks::unlock()
 {
     for (list<FDPair>::iterator i = fds.begin(); i != fds.end(); i++) {
         if (deletePaths) deleteLockFilePreClose(i->second, i->first);
@@ -216,6 +222,8 @@ PathLocks::~PathLocks()
 
         debug(format("lock released on `%1%'") % i->second);
     }
+
+    fds.clear();
 }
 
 
diff --git a/src/libstore/pathlocks.hh b/src/libstore/pathlocks.hh
index 8b4100028..9898b497b 100644
--- a/src/libstore/pathlocks.hh
+++ b/src/libstore/pathlocks.hh
@@ -36,6 +36,7 @@ public:
     void lockPaths(const PathSet & _paths,
         const string & waitMsg = "");
     ~PathLocks();
+    void unlock();
     void setDeletion(bool deletePaths);
 };