X-Git-Url: http://www.chiark.greenend.org.uk/ucgi/~ian/git?p=chiark-utils.git;a=blobdiff_plain;f=scripts%2Fgit-cache-proxy;h=b4b23001cb3ed42686ccaf0c1392c7f4f0bc40c5;hp=520f1e5f28c8cbdf9a2cb0a4406f5d386f974a6e;hb=32c189107d19892ab4730757003c07576f139de5;hpb=eda343442f5440c4a4b23fd2cdf9bd8cb6953761

diff --git a/scripts/git-cache-proxy b/scripts/git-cache-proxy
index 520f1e5..b4b2300 100755
--- a/scripts/git-cache-proxy
+++ b/scripts/git-cache-proxy
@@ -157,6 +157,31 @@ for (;;) {
 
 #---------- utility functions ----------
 
+sub lockfile ($$) {
+    my ($fh, $fn, $flockmode) = @_;
+    for (;;) {
+	close $fh;
+	open $fh, '+>', $fn or fail "open/create $fn for lock: $!";
+	if (!flock $fh, $lockmode) {
+	    if ($lockmode & LOCK_NB and $! == EWOULDBLOCK) {
+		return 0; # ok then
+	    }
+	    fail "lock $fn".
+		(($flockmode & ~LOCK_NB) == LOCK_SH ? " (shared)" : "").
+		": $!";
+	}
+	stat $fh or fail "stat opened $fn: $!";
+	my $fh_ino = ((stat _)[1]);
+	if (!stat $fn) {
+	    $! == ENOENT or fail "stat $fn: $!";
+	    next;
+	}
+	my $fn_ino = ((stat _)[1]);
+	return 1 if $fn_ino == $fh_ino;
+	# oh dear
+    }
+}
+
 sub xread {
     my $length = shift;
     my $buffer = "";
@@ -236,8 +261,7 @@ sub readcommand () {
 }
 
 sub clonefetch () {
-    open LOCK, "+>", $lock or fail "open/create $lock: $!";
-    flock LOCK, LOCK_EX or fail "lock exclusive $lock: $!";
+    lockfile \*LOCK, $lock, LOCK_EX;
 
     my $exists = lstat $gitd;
     $exists or $!==ENOENT or fail "lstat $gitd: $!";
@@ -315,10 +339,7 @@ sub clonefetch () {
     }
 
     servinfo "sharing";
-    flock LOCK, LOCK_UN or fail "unlock $lock: $!";
-    flock LOCK, LOCK_SH or fail "lock shared $lock: $!";
-    # actually, just relocking as shared would have the same semantics
-    # but it's best to be explicit
+    lockfile \*LOCK, $lock, LOCK_SH; # NB releases and relocks
 
     if (chdir $gitd) {
 	return 1;
@@ -356,10 +377,9 @@ sub housekeeping () {
 
 sub housekeepingcheck ($$) {
     my ($dofork, $force) = @_;
-    open HLOCK, "+>", "Housekeeping.lock" 
 	or fail "open/create Housekeeping.lock: $!";
     if (!$force) {
-	if (flock HLOCK, LOCK_EX|LOCK_NB) {
+	if (!lockfile \*HLOCK, "Housekeeping.lock", LOCK_EX|LOCK_NB) {
 	    logm 'debug', "housekeeping lock taken, not running";
 	    close HLOCK;
 	    return 0;