Re: [PATCH v2] pack-objects: Use packing_data lock instead of read_mutex

From: Patrick Hogg <phogg@novamoon.net>
Date: Jan 22, 2019, 23:54 UTC
Message-ID: <CAFOcBz==BunV48U94ZSnc2gmBTOcOpY4XO-dPugKMUVNZGjzZA@mail.gmail.com>
In-Reply-To: <xmqq1s54e2ju.fsf@gitster-ct.c.googlers.com>

On Tue, Jan 22, 2019 at 5:43 PM Junio C Hamano <gitster@pobox.com> wrote:

Show 21 quoted lines

>
> Patrick Hogg <phogg@novamoon.net> writes:
>
> > As I mentioned in the prior thread I think that it will be simpler
> > to simply use the existing lock in packing_data instead of moving
> > read_mutex. I can go back to simply moving read_mutex to the
> > packing_data struct if that that is preferable, though.
>
> I'll let others comment on this to show preference between the two
> approaches.
>
> > I also removed the #ifndef NO_PTHREADS in prepare_packing_data around
> > the initialization of &pdata->lock since I had to upgrade the lock to
> > a recursive mutex. As far as I can tell init_recursive_mutex (and
> > pthread_mutex_init for that matter) have that protection already so it
> > appears to be redundant.
>
> If you can defer "I also" to a separate patch, please do so.
> Keeping the fix alone as small as possible and not tangled with
> other changes would make it easier for people to cherry-pick the fix
> to older maintenance tracks if they choose to.

That's a fair point. To confirm (as I'm rather new to submitting git patches), do you mean to submit a two-patch series or to just leave out the #ifndef removal altogether for now?

If this does become a two patch series I could simply move the read_mutex to packing_data in the first patch and merge the two mutexes (and remove the #ifndef) in the second. That would keep the fix alone even smaller (just the first patch) to simplify cherry-picking.

(There is also the option of going back to the v1 change and correcting the cleanup in the early return.)

I just want to confirm preferences first before submitting a v3 to avoid spamming patches; I'll go whichever way the experts think is best.

Thanks, -Patrick