"Jay Soffian" <jaysoffian@xxxxxxxxx> writes:
> On Thu, Mar 13, 2008 at 7:14 PM, Petr Baudis <pasky@xxxxxxx> wrote:
>
> ...
>
> > + if ($cache_lifetime and -f $cache_file) {
> > + # Postpone timeout by two minutes so that we get
> > + # enough time to do our job.
> > + my $time = time() - $cache_lifetime + 120;
> > + utime $time, $time, $cache_file;
> > + }
>
> Race condition. I don't see any locking. Nothing keeps multiple
> instances from regenerating the cache concurrently...
>
> > + @projects = git_get_projects_details($projlist, $check_forks);
> > + if ($cache_lifetime and open (my $fd, '>'.$cache_file)) {
>
> ...and then clobbering each other here. You have two choices:
>
> 1) Use a lock file for the critical section.
>
> 2) Assume the race condition is rare enough, but you still need to
> account for it. In that case, you want to write to a temporary file
> and then rename to the cache file name. The rename is atomic, so
> though N instances of gitweb may regenerate the cache (at some
> CPU/IO overhead), at least the cache file won't get corrupted.
What should the code for this look like? Like below?
use File::Temp;
my ($fh, $temp_file) = tempfile();
...
close $fh;
rename $temp_file, $cache_file;
--
Jakub Narebski
Poland
ShadeHawk on #git
--
To unsubscribe from this list: send the line "unsubscribe git" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
