Re: git .lock file error
- From
Ævar Arnfjörð Bjarmason <avarab@gmail.com>
- Date
- Sep 30, 2010, 21:16 UTC
- Message-ID
- <AANLkTi=H0vhNJTT9uWYXmy=45_wrvb0xwjRSHvAETiAB@mail.gmail.com>
- In-Reply-To
- <AANLkTinFJ5rSA7Om0ZxhuqzQiqEDvJ+JoEQFpz=NDvxE@mail.gmail.com>
On Thu, Sep 30, 2010 at 21:10, Nate Parsons <parsons.nate@gmail.com> wrote:
Show 22 quoted lines
> On Thu, Sep 30, 2010 at 4:15 PM, Junio C Hamano <gitster@pobox.com> wrote:
>> Ævar Arnfjörð Bjarmason <avarab@gmail.com> writes:
>> > FWIW I think this is more readable, but maybe we want to retry on all
>> > platforms:
>> >
>> > my $fh;
>> > if ($^O eq 'MSWin32' or $^O eq 'cygwin') {
>> > # Try 10 times to open our lock file, in case Windows is lagging
>> > for my $try (1..10) {
>> > sysopen($fh, $db_lock, O_RDWR | O_CREAT);
>> > last if $fh;
>> > }
>> > } else {
>> > sysopen($fh, $db_lock, O_RDWR | O_CREAT);
>> > }
>> >
>> > warn "Couldnt open $db_lock: $!\n" unless $fh;'
>
> I agree that this is more readable, although I don't think there needs
> to be separate code sections for each OS. If it's a good OS, it will
> only loop once. You would want to die or croak instead of warn,
> though. It needs the lock to continue, right?Yes, right. Meant to write croak() not warn() there.
Show 21 quoted lines
>> What exactly does "Windows is lagging" mean in the above? >> >> Why does sysopen() randomly fail and why does it succeed (sometimes) when >> it immediately gets retried with the same argument? Is this a shared lock >> and is used by some other processes that drive git? Why does the issue >> manifest only on Windows? If there are competing processes, wouldn't it >> exacerbate the situation to run a tight loop to try grabbing the lock >> without waiting, like the above patch does? > > All very good questions, and I don't know most of the answers. I know > that sysopen() is just a thin wrapper around the 'open' system call, > so the problem has to be with Windows somehow. It probably doesn't > happen with other OSes because they're better at files :P > > I have verified (to the best of my ability) that this problem happens > even when TortoiseGit is not running, and I don't have cheetah > installed, and there are no other 'git.exe's running. I considered > putting some sort of sleep() in there, but since it worked so well > without the sleep (it only retried once at most). Fetching multiple > revisions is slow anyways, so I don't think a 2-second wait would > hurt, though.
Maybe this has to do with our assumptions about being on a POSIX filesystem, doesn't Windows have different semantics if two processes open the same file, or something?
Blah, I don't know. I'm about as clueless when it comes to Windows as VMS :)