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Make 'cvs ci' lockless in git-cvsserver by using git-update-ref 

This makes "ci" codepath lockless by following the usual
"remember the tip, do your thing, then compare and swap at the
end" update pattern using update-ref.  Incidentally, by updating
the code that reads where the tip of the head is to use
show-ref, it makes it safe to use in a repository whose refs are
pack-pruned.

I noticed that other parts of the program are not yet pack-refs
safe, but tried to keep the changes to the minimum.

Signed-off-by: Junio C Hamano <junkio@cox.net>
This commit is contained in:
Junio C Hamano 2007-02-20 21:54:39 -08:00
parent 4e4b55dd0f
commit ada5ef3b48
1 changed files with 16 additions and 27 deletions
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43
git-cvsserver.perl
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@ -1031,36 +1031,35 @@ sub req_ci
exit;
}
my $lockfile = "$state->{CVSROOT}/refs/heads/$state->{module}.lock";
unless ( sysopen(LOCKFILE,$lockfile,O_EXCL|O_CREAT|O_WRONLY) )
{
$log->warn("lockfile '$lockfile' already exists, please try again");
print "error 1 Lock file '$lockfile' already exists, please try again\n";
exit;
}
# Grab a handle to the SQLite db and do any necessary updates
my $updater = GITCVS::updater->new($state->{CVSROOT}, $state->{module}, $log);
$updater->update();
my $tmpdir = tempdir ( DIR => $TEMP_DIR );
my ( undef, $file_index ) = tempfile ( DIR => $TEMP_DIR, OPEN => 0 );
$log->info("Lock successful, basing commit on '$tmpdir', index file is '$file_index'");
$log->info("Lockless commit start, basing commit on '$tmpdir', index file is '$file_index'");
$ENV{GIT_DIR} = $state->{CVSROOT} . "/";
$ENV{GIT_INDEX_FILE} = $file_index;
# Remember where the head was at the beginning.
my $parenthash = `git show-ref -s refs/heads/$state->{module}`;
chomp $parenthash;
if ($parenthash !~ /^[0-9a-f]{40}$/) {
print "error 1 pserver cannot find the current HEAD of module";
exit;
}
chdir $tmpdir;
# populate the temporary index based
system("git-read-tree", $state->{module});
system("git-read-tree", $parenthash);
unless ($? == 0)
{
die "Error running git-read-tree $state->{module} $file_index $!";
}
$log->info("Created index '$file_index' with for head $state->{module} - exit status $?");
my @committedfiles = ();
# foreach file specified on the command line ...
@ -1095,8 +1094,6 @@ sub req_ci
{
# fail everything if an up to date check fails
print "error 1 Up to date check failed for $filename\n";
close LOCKFILE;
unlink($lockfile);
chdir "/";
exit;
}
@ -1139,16 +1136,12 @@ sub req_ci
{
print "E No files to commit\n";
print "ok\n";
close LOCKFILE;
unlink($lockfile);
chdir "/";
return;
}
my $treehash = `git-write-tree`;
my $parenthash = `cat $ENV{GIT_DIR}refs/heads/$state->{module}`;
chomp $treehash;
chomp $parenthash;
$log->debug("Treehash : $treehash, Parenthash : $parenthash");
@ -1165,8 +1158,6 @@ sub req_ci
{
$log->warn("Commit failed (Invalid commit hash)");
print "error 1 Commit failed (unknown reason)\n";
close LOCKFILE;
unlink($lockfile);
chdir "/";
exit;
}
@ -1179,14 +1170,17 @@ sub req_ci
{
$log->warn("Commit failed (update hook declined to update ref)");
print "error 1 Commit failed (update hook declined)\n";
close LOCKFILE;
unlink($lockfile);
chdir "/";
exit;
}
}
print LOCKFILE $commithash;
if (system(qw(git update-ref -m), "cvsserver ci",
"refs/heads/$state->{module}", $commithash, $parenthash)) {
$log->warn("update-ref for $state->{module} failed.");
print "error 1 Cannot commit -- update first\n";
exit;
}
$updater->update();
@ -1215,12 +1209,7 @@ sub req_ci
}
}
close LOCKFILE;
my $reffile = "$ENV{GIT_DIR}refs/heads/$state->{module}";
unlink($reffile);
rename($lockfile, $reffile);
chdir "/";
print "ok\n";
}