Potential deadlock in PCRE cache

[tstarling]

In 2014 I improved HHVM's PCRE compilation cache, introducing a new thread-safe container to hold cache entries. I also published the container class as a separate library. Another user of the library reported a deadlock issue, and it appears that it may also affect HHVM. If an application uses many different regexes and traffic is heavy, HHVM may globally deadlock. I'm not an HHVM user anymore, but out of courtesy I am forwarding the issue. The deadlock issue is discussed at tstarling/thread-safe-lru#5 and the proposed fix is tstarling/thread-safe-lru#6 .

[lexidor]

Adding probably easy. The fix presented in starling/thread-safe-lru#6 is a one liner (releasing a lock). This could be easily integrated into hhvm. The patch is licensed under Apache2. This is a simple copy paste fix.

I am not sure this reproduces in the context of hhvm.

I feel bad for the fact that your gesture went unanswered for 1½ years. The fact that you support a patch you made to hhvm a decade ago after leaving hhvm behind is truly commendable.