From e0d7e47862aa1b33292fb8d05e5d50ad4ebf3590 Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <e.dolstra@tudelft.nl>
Date: Tue, 28 Aug 2007 09:39:03 +0000
Subject: [PATCH] * PathLocks::lockPaths: don't allow reacquiring a lock we
 already   hold.

---
 src/libstore/gc.cc        | 4 +++-
 src/libstore/pathlocks.cc | 6 ++----
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 8ce717aaff..e2e6c23fd5 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -61,6 +61,8 @@ void createSymlink(const Path & link, const Path & target, bool careful)
     /* Create directories up to `gcRoot'. */
     createDirs(dirOf(link));
 
+    /* !!! shouldn't removing and creating the symlink be atomic? */
+
     /* Remove the old symlink. */
     if (pathExists(link)) {
         if (careful && (!isLink(link) || !isInStore(readLink(link))))
@@ -68,7 +70,7 @@ void createSymlink(const Path & link, const Path & target, bool careful)
         unlink(link.c_str());
     }
 
-    /* And create the new own. */
+    /* And create the new one. */
     if (symlink(target.c_str(), link.c_str()) == -1)
         throw SysError(format("symlinking `%1%' to `%2%'")
             % link % target);
diff --git a/src/libstore/pathlocks.cc b/src/libstore/pathlocks.cc
index 03ba4f2124..821d4d02fe 100644
--- a/src/libstore/pathlocks.cc
+++ b/src/libstore/pathlocks.cc
@@ -161,10 +161,8 @@ void PathLocks::lockPaths(const PathSet & _paths, const string & waitMsg)
 
         debug(format("locking path `%1%'") % path);
 
-        if (lockedPaths.find(lockPath) != lockedPaths.end()) {
-            debug(format("already holding lock on `%1%'") % lockPath);
-            continue;
-        }
+        if (lockedPaths.find(lockPath) != lockedPaths.end())
+            throw Error("deadlock: trying to re-acquire self-held lock");
 
         AutoCloseFD fd;