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authorEelco Dolstra <e.dolstra@tudelft.nl>2011-04-11T12·40+0000
committerEelco Dolstra <e.dolstra@tudelft.nl>2011-04-11T12·40+0000
commit08c89714984ca64b9ddfe53c99254c70a784e81c (patch)
treee22cafe17c17b1d6df65db16de1fa16c82d5c5b6 /scripts/NixManifest.pm.in
parentb2c11b9ed05d33bb938d83fbcb367256427450f6 (diff)
* Lock the database during updates.
Diffstat (limited to 'scripts/NixManifest.pm.in')
-rw-r--r--scripts/NixManifest.pm.in9
1 files changed, 8 insertions, 1 deletions
diff --git a/scripts/NixManifest.pm.in b/scripts/NixManifest.pm.in
index 4dda69710d7f..20749acd7e40 100644
--- a/scripts/NixManifest.pm.in
+++ b/scripts/NixManifest.pm.in
@@ -3,6 +3,7 @@ use DBI;
 use Cwd;
 use File::stat;
 use File::Path;
+use Fcntl ':flock';
 
 
 sub addPatch {
@@ -259,7 +260,11 @@ EOF
 
     $dbh->do("create index if not exists Patches_storePath on Patches(storePath)");
 
-    # !!! locking?
+    # Acquire an exclusive lock to ensure that only one process
+    # updates the DB at the same time.  This isn't really necessary,
+    # but it prevents work duplication and lock contention in SQLite.
+    open MAINLOCK, ">>$manifestDir/cache.lock" or die;
+    flock(MAINLOCK, LOCK_EX) or die;
 
     # Read each manifest in $manifestDir and add it to the database,
     # unless we've already done so on a previous run.
@@ -326,6 +331,8 @@ EOF
 
     $dbh->commit;
 
+    close MAINLOCK;
+
     return $dbh;
 }