bug#34910: 27.0.50; Too much matching reentrancy

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Cc: dancol@dancol.org, 34910@debbugs.gnu.org
> Date: Tue, 19 Mar 2019 13:25:13 +0100
> 
> It turns out the regexp cache logic is broken: it always uses the last
> (LRU) entry, and fails if that entry is busy. It should really use the
> last free entry.
> 
> What happened was that a regexp failed because of stack overflow, which
> caused lots of code to run and many regexps to be compiled, but the
> original (failing) regexp was still marked busy in the cache.
> Eventually, it had been pushed down to the last position in the cache,
> where it caused the next request for a free cache entry to fail with
> the reentrancy error.
> 
> This patch fixes it. Please review.

Since there were no further comments, I think you should push this.

Thanks.