Re: [PATCH/RFC] grep: turn off threading when recursing submodules

From: Jeff King <peff@peff.net>
Date: Oct 19, 2017, 19:34 UTC
Message-ID: <20171019193413.prx5pkmwaxk6mpdt@sigill.intra.peff.net>
In-Reply-To: <20171019192618.GB84767@google.com>

On Thu, Oct 19, 2017 at 12:26:18PM -0700, Brandon Williams wrote:

Show 10 quoted lines

> One alternative to turning off threading would be to employ proper
> locking (like I failed to do) by wrapping the call the
> 'add_to_alternates_memory()' in calls to grep_read_lock/unlock:
> 
>   +       grep_read_lock();
>           add_to_alternates_memory(submodule.objectdir);
>   +       grep_read_unlock();
> 
> That way adding the submodule to the object database won't happen at the
> same time another thread is trying to read from the object store.

Yeah, I think that is the right approach. Many of Git's APIs aren't thread-safe, so we need a big mutex around "I am doing anything except actually looking at the already-read blob contents". We just missed this spot.

-Peff